How to fix Computer Viruses

A virus is a computer program written by nefarious individuals with the malicious intention of altering the way a system operates without the knowledge of the people who use the system. The virus is capable of executing and rewriting itself. The reason why people dread viruses is that they can wreck havoc on the system. They can corrupt or delete files, render programs useless and can even reformat the hard disk which can result in data loss and system crashes.

How Viruses Can Get On To Your System

Viruses can find their way to your system by several methods. You can get viruses as attachments with emails and instant messages. When you open these attachments they can infect your systems. When you download and open a program from the internet that has been infected and when you share a file over a server that has been infected you risk infecting your own system. It can also transmit through infected removable disks.

Types Of File Viruses

There are many different types of viruses that can be classified based on their mode of infection, the area of infection and the method used to select a system to infect. There are viruses that infect the files, boot sectors, script hosts and macro environments.

Viruses that infect the file system are further sub-divided into various types. File viruses infect files using various methods. The simplest method is to overwrite the code of the infected file. This makes the file unusable and can result in system crash.

There are files that modify the code of the infected file and the file is not rendered useless, it remains partially or fully functional and such a virus is called a parasitic virus. The malicious code can be written either at the beginning, the ending or in the middle of the file. There are files that write themselves on to gaps present in the file or the empty sectors found in the file. Each time the file is accessed they ensure that the malicious command is also executed. These files need to have the right entry point in order to be executed soon or they may remain dormant for a very long time and can also be deleted before they can infect the system.

Companion viruses are file viruses that do not modify the original file that they infect instead create a duplicate file with the malicious code. When the original file is being accessed, the virus makes sure that the duplicate file with the virus gets executed.

There are files that copy themselves onto various directories and lie dormant until they are executed. There are certain viruses that modify the file system in such a fashion that the infected file is executed. These are termed as link viruses.

The boot sector and master boot record viruses are memory residents. They can infect the system when an infected disk is read on the system.  Multi-parasite viruses infect program files as well as the boot records. Both these viruses infect the start up files.

Macro viruses are those that infect data files. These files can be written in such a fashion that the other file apart from data files can be infected. They infect Microsoft PowerPoint, Excel, Word and Access files.

Script viruses are viruses that are written in script languages that infect other script files.

When the viruses infect the system it slows down without any explanation, it behaves erratically displaying error messages and you might find programs or certain files missing. Some files may not open and you may find some programs do not function as they should. The best way to deal with virus threats is to use an updated anti-virus that can scan and keep your system virus-free.

Computer viruses are programs which are designed to infect files on your computer. How do computer viruses work and how do they infect files? Let’s take a look at some of the basic details about computer viruses and find out how we can protect our computers from viruses and have a safe time on the world wide web!

A computer virus is just a piece of computer code - the only way that it can infect your computer is if you run something which has the virus in it. Certain kinds of files that you can download and run are called executable files. This is just a fancy name for the kind of file that you double click on to start a program. A computer virus can hide inside one of these executable files and when you run the file it will be activated - some computer viruses will then stay in the memory of your computer while others will carry out some infection task and then quit.

Typically a computer virus will not have an immediately visible effect. Computer viruses which do something to change your system right away are quickly caught, and most viruses which survive on the world wide web are designed so that they spread a certain amount before they do anything which could be harmful. There are even benign computer viruses which do nothing but copy themselves and which do not do anything harmful to the computers which they infect. It’s best to avoid any and all kinds of computer viruses however, as even these small ones take up a small amount of processing power and memory and can slow your system.

Often, a computer virus will be appended to the beginning of an executable file. When the file is run, the virus will run first, do whatever it is that it is instructed to do when the program it is attached to is started, and then the ordinary program will run its course. Perhaps when you run the virus program it will copy itself to another file on your hard drive by doing a quick search for executable files and then appending a copy of itself to another program.

Viruses will not always attach themselves to the beginnings of programs - they may choose to place themselves inside or at the end of programs. A reference or jump will then be added to the beginning of the program so that the virus will still be accessed first when the program is started. This is just one kind of trick that virus writers developed years ago to try and make it harder for anti-virus programs to detect their work.

There are lots of other tricks that viruses use to infect files, such as self-encryption to keep them from being identified. Viruses have even been developed which can infect certain kinds of scripting and not just executable files. By keeping an anti-virus program up to date on your computer (so that it can identify all of the newest tricks) and using it regularly you can catch most viruses and keep your computer safe!

How do computer viruses infect files - it is a question which has many possible answers, as there are thousands and thousands of computer viruses in existence and they all have somewhat different infection techniques. In the past the ways in which computer viruses would infect files was simpler - when computer viruses were first invented most of the basic computer viruses would attach themselves to the beginning of an executable file and be run first whenever the program would start. Each time that the program would run the computer viruses would search for more programs to infect and attach themselves to the beginnings of those, and so on.

More advanced types of computer viruses started to emerge as the years went by. The computer viruses which would simply attach themselves to the beginnings of programs without any other methods to protect themselves were quickly identified and defeated, so computer viruses were designed which wrote themselves to other parts of the file. The new computer viruses would put themselves at the end or somewhere in the middle of a program file. Some anti-virus programs could still detect them, though, because of the appearance of their code.

This led to computer viruses which used encryption on themselves so that they would not be seen by anti-virus software. The encryption would be a little different each time and this would make it harder for an anti-virus program to identify the unique signature of a virus. Anti-virus programs still had ways of finding the computer viruses, however - they could look at the way that a program flowed and determine whether there was a part which was suspicious. They could also compare versions of a program and recognize when a change had been made.

Some kinds of computer viruses have been created which change not only their encryption and appearance but their behavior as well. These kinds of morphing computer viruses can be more difficult to track and more difficult to come up with anti-virus software to defend against. However, new and modern anti-virus software is designed not only with virus signatures included but with heuristic (rule-based) software as well. This software is good at identifying what a program does no matter how it looks, and it is a good way to get the harder types of computer viruses which elude capture.

The most common kind of file for a computer virus to infect is a program file, also known as an executable file. Sometimes computer viruses will not occupy the program file themselves, but will occupy some kind of fake DLL file which will be called by various programs. There are also new computer viruses created today which can reside in data files when those data files are capable of being filled with scripting commands for the programs which read them.

One way to keep ahead of the developments in computer viruses is to have an anti-virus program which is kept current. Another way is to be generally careful about your computer and not run programs unless you know they are from a reputable source. Good luck staying safe from computer viruses on the world wide web!