Antivirus

An antivirus is utility software which detects and removes computer viruses. If the

software is not able to remove the virus, it is neutralized. The antivirus keeps a

watch on the functioning of the computer system. If a virus is found it may alert

the user, flag the infected program or kill the virus. Some of the common types of

viruses are:

 Boot Sector Virus: A boot sector virus displaces the boot record and copies

itself to the boot sector i.e. where the program to boot the machine is stored.

So first the virus is loaded on to the main memory and then the operating

system. Whenever a new disk is inserted the virus copies itself to the new

disk. The antivirus overwrites the correct boot record on the infected boot

sector and also cleans the bad sectors.

 File Virus: A file virus generally attacks executable files. They can attach to

various locations of the original file, replace code, fill in open spaces in the

code, or create companion files to work with an executable file. Most of the

file viruses are memory resident and wait in the memory until the user runs

another program. While another program is running, the virus replicates.

 Macro Virus: This virus infects an important file called normal.dot of MS

Word. As soon as the application is opened the virus gets activated. It

damages the formatting of documents and even may not allow editing or

saving of documents.

 Trojan Horse: It is a code generally hidden in games or spreadsheets. Since

they are hidden, the program seems to function as the user wants but

actually, it is destroying the program. A Trojan horse does not require a host

program to embed itself. It is a complete program. Its main objective is to

cause harm to the data. They can create bad sectors on the disk, destroy file

allocation tables and cause the system to hang.

 Worm: Worm is a program capable of replicating itself on a computer

network. A worm also does not require a host as it is a self-contained

program. They generally travel from one computer to another across

communication links on a network. They generally disrupt routine services.

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