Types of Computer Virus:-

Boot viruses

Since nobody uses floppy disks anymore, these types of computer virus are left to infect only the master boot records of the hard disk. The boot record program loads the operating system in the memory at startup. These viruses replace the boot record and move it to a different part of the hard disk, or simply overwrite it. As you can imagine, once you start your operating system, it loads into memory, along with the virus. Once the virus is in the memory, it is free to do whatever it was programmed to do. To avoid loading the boot record viruses into memory, you must boot your operating system from another source (another hard drive or a bootable CD/DVD).

Program viruses

These types of computer virus will infect only executable files (with extensions like .BIN, .COM, .EXE, .OVL, .DRV, and .SYS). Once executed, these programs load into memory, along with the virus contained within them. Once in the memory, the scenario repeats – the virus is free to act and infect other files or simply deliver its payload. These viruses are friendlier than boot viruses and can be removed a lot easier.

Multipartite viruses

These computer viruses are hybrids, derived from boot viruses and program viruses. They infect executable files, just like the program viruses but, once the executable is executed, it infects the master boot records. The scenario is similar to the boot virus’s one: once you boot your operating system, the virus is loaded into the memory, from where it is free to infect other programs and replicate itself, ultimately delivering the payload.

Stealth viruses

These viruses are specialized in avoiding detection and will use a number of techniques to do so. Most of them simply redirect the hard disk head, forcing it to read another memory sector instead of their own. Some of them also alter the reading of the file size shown when listing the directory. These types of computer virus are very hard to find by humans, but antivirus software is specially designed to track them down and erase them.

Polymorphic viruses

The polymorphic viruses will always change their source code from one infection to another. Each infection is different, and this makes detection very hard. However, detection is still possible, depending on the antivirus.

Macro viruses

This virus is relatively new and it infects macros within a template or document. When you open a word processing document, it activates the virus. The virus infects the Normal.dot template, which is a general file used by all the documents. So, whenever you open an uninfected document, by referring to the Normal.dot file, it gets infected as well. This infection can only spread if infected documents are opened on another machine.

Active X viruses

Most people do not know how to configure ActiveX and Java controls, unconsciously leaving a security hole. Applets are then allowed to run freely on the machine, delivering all ActiveX viruses. By simply turning off some ActiveX and Java controls in the browser, a user can efficiently protect their PC from this type of computer virus.

Krish Infotech Lesson: How To Add Watermark to a Word Document

Step-by-step to add a watermark to Word document (applied for Microsoft Word 97-2010):

Microsoft Word 97/2000/XP (2002)/2003:

Open the Word document that you want to add watermark to.
Select "Format" from the top menu, then select "Background", then "Printed Watermark".
In the "Printed Watermark" dialog:

A. To insert a text watermark:
Select the "Text watermark".
Then, either select a pre-defined text from the drop-down, or type in your desire text on the "Text" field.
Customize your watermark with other options in this dialog such as text size, text color, etc, then click "OK".
Watermark is now inserted into your document.

B. To insert an image watermark:
Select the "Picture watermark".
Then click on the button "Select Picture...".
Navigate to the directory where your watermark picture is located. Select it and click "Insert".
Select a customized scale if desired, then click "OK".
The image is now inserted into your document as watermark.



Microsoft Word 2007/2010:

Open the Word document that you want to add watermark to.
Select the "Page Layout" Tab from the top menu
In the "Page Background" group, select "Watermark".
You can now select one of the pre-defined watermarks, or if you wish to use your own text/image, select "Custom Watermark" at the bottom.
At the "Printed Watermark" dialog:

A. To insert a text watermark:
Select the "Text watermark".
Then, either select a pre-defined text from the drop-down, or type in your desire text on the "Text" field.
Customize your watermark with other options in this dialog such as text size, text color, etc, then click "OK".
Watermark is now inserted into your document.

B. To insert an image watermark:
Select the "Picture watermark".
Then click on the button "Select Picture...".
Navigate to the directory where your watermark picture is located. Select it and click "Insert".
Select a customized scale if desired, then click "OK".
The image is now inserted into your document as watermark.

Krish Infotech: PC Shortcut Keys

Computer Tips: How to Improve Your Computer’s Performance

Few things are as frustrating as dealing with a slow, sluggish computer. When a computer is brand new, it works wonderfully well. Over time, though, its performance can slowly begin to worsen. This happens for a number of reasons, but the biggest culprits are things like spyware, adware and other computer threats that are unwittingly downloaded along with other content while online. You don’t have to download thousands of MP3s, movies or other items to experience these problems, either – nobody is immune to them. Instead of accepting the situation, there are plenty of techniques and strategies that you can use to make it better – a few of the best ones are outlined below.

Strategy #1: Clean Your Computer’s Windows Registry

The biggest cause of slow, sluggish PC performance is errors and problems within its Windows registry. Adware, spyware and other threats usually target the registry, damaging or misplacing important files within it. When it comes to PC cleaning, a daily Windows registry cleaning should be at the top of your list of priorities. However, this should never be done manually – there are too many opportunities for major errors that could seriously damage your PC’s operating system. Instead, invest in a high-quality Windows registry cleanup program and configure it to run once per day – you won’t believe the difference that it makes.

Strategy #2: Remove Unneeded Files

Every time you log on to the Internet or otherwise use your computer, temporary files are generated. They are usually only needed once; however, they don’t disappear on their own. Instead, they accumulate over time until they are cluttering up your computer’s file system and affecting its performance. While it’s possible to remove these files one-by-one, it’s much easier and quicker to use a PC cleaning tool that’s designed for the purpose. Try to do so about one time per week to keep your computer humming along with ease.

Strategy #3: Remove Unneeded Programs

Like many people, you probably download and try out many different programs each month. How many of them do you actually end up using on a regular basis? Chances are, not very many of them. By getting into the habit of uninstalling unused and unneeded programs, you can keep your computer’s file system a lot less cluttered. In turn, your PC’s performance will improve dramatically. You can optimize your computer in this way by using its Add/Remove Programs feature. Its location varies by operating system, but you should be able to find it somewhere in the Control Panel.

Strategy #4: Empty the Recycle Bin

When you click “delete” on a file or a program, it doesn't go away for good – not immediately, anyway. Instead, it sits in a kind of purgatory in your computer’s Recycle Bin. As things pile up in the Recycle Bin, your computer can start exhibiting some very annoying problems. If sluggish start ups and frequent crashes are occurring with increasing frequency – and your computer’s recycle bin is very full – go ahead and empty it. From then on, get into the habit of doing so about one time per week. This small but important strategy can make a huge difference.

Strategy #5: Perform a Disk Defragmentation

Windows isn’t very efficient when it comes to storing files. It actually splits them up, depositing them into whatever spaces are available. The more spaced apart the pieces of a file are, the harder your computer has to work to make them run. The Windows disk defragmentation system tune-up utility works to piece all of those files back together again. The process is a long one, though, and only needs to be done about four times per year. Set it up to run automatically once every three months. By doing so, you’ll be able to keep your computer running in tiptop shape.

When it comes to keeping your computer running optimally, small but regular maintenance is the best way to go. Protecting your PC only does so much; even the most careful Internet users in the world unintentionally download malicious software from time to time. By using basic system tune-up tools, cleaning your computer’s Windows registry regularly, performing regular file-cleaning maintenance and otherwise optimizing your PC, you should be able to keep it in like-new condition for a lot longer. Even if your computer has been performing slowly for some time, beginning this regimen is sure to produce results. In the end, you’ll be able to enjoy a computer that flies along – instead of one that spins its wheels.

Still you have problem...

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