What is computer virus ?
What is computer virus ?
A computer virus is a program that spreads across computers by attaching a copy of itself to the files on your computer. When you run the infected file the virus get into action.
A virus is usually harmful and can corrupt data, overwrite files, or use up system resources, and slow it down in the process. Some may be merely disturbing like asking you to key in certain messages to continue or popping up messages on the screen.
Where do viruses come from ?
Viruses are usually written by programmers to cause trouble.
Types of Viruses:
- Viruses which attack certain area or location.
- Viruses which attack in a particular manner
The major types identified depending on the area they infect are:
- Boot sector viruses:There viruses infect the boot sector of disks. A boot sector stores the programs that have to be executed when you start your PC. By infecting this area of a disk, the virus loads itself whenever you Boot with that disk. If then remains in your PC's memory and infects any other disk you use on your system. There's a more dangerous virus type you've to watch out for-the partition Sector virus. It says in an area called the master boot record which stores the information about the partition on your hard drive. The partition sector also has a program that is run every time you power up your PC so when you start your PC the virus is loaded into memory straight away some viruses also encrypt the contents of the master boot record this makes removal of the virus dangerous removing it might mean that the contents of your hard disk cannot be accessed anymore (since only the virus can decrypt the MBR contents).
- File viruses: These are by far the most infectious kind. File viruses attach a copy of themselves onto the beginning of an executable file (files with a .COM or .EXE extension ). When you run the infected file, the virus code get executed. The most intelligent viruses then execute the actual file- so everything appears normal. But virus is now in your PC's memory. When another "clean" executable file is run, the virus attaches itself to that file. It soons infects most of the programs on your hard disk. So, all your precious data is at great risk.
- Cluster viruses:Cluster viruses store a single virus copy in a certain area on the disk. Then they change the DOS directory information so that the location of each program in the File Allocation Table (FAT) points to the area where the virus sits . When you run a program the virus gets to work and then it runs the original program and this increases the chances of your data getting corrupted.
The main ones that attack computers in peculiar manner:
- Stealth viruses: These viruses try to conceal their presence by hiding the modification they make. When any application asks for some disk information-file sizes, free disk space, and so on- the virus in intercepts it and gives back the original information instead of the actual information.
- Polymorphic viruses:Most virus scanners look for "search strings" within a program to detect viruses. Polymorphic viruses encrypt their code on each infection so that the virus codes of two infected files don't look the same. So detecting these viruses is much harder.
- Multipartite viruses: These are particularly nasty. They can infect both the boot sector as well as files. So they spread much more quickly than other viruses. Fortunately, their occurance is rare.
- Fast, slow, and sparse infecting viruses: A fast infecting virus infects files whenever they are accessed. So whenever you read a file, or write or modify it, or just do a directory listing the file gets infected. This makes them easier to detect but they can be dangerous too. When you run a virus scan all files are read . If your virus scanner is outdated and can't catch virus , your entire hard disk will be infected.
Use your anti-virus effectively:
Check for features before investing in virus protection software.
Use good anti-virus software:
To nail the bugs in your PC, use a good anti-virus software
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