All About Viruses

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How Virus Works
1)How Boot Viruses Strikes.
a)The user unsuspectingly copies a virus infected file on floppy disk or hard disk.
b)When the infected file is executed it is loaded with the virus into RAM.
c)The Virus copied the boot record program to another sector and puts a pointer to it in the boot sector. Then the virus makes a copy of itself in disk boot sector. The next time coputer boots from this disk, the virus in the boot sector loads itself in to RAM, makes copy of itself and infect another files.
2)How Polymorphic Viruse Strikes.
a)The user copies an infected file to disk.
b)When the infected file is executed it is loaded with the virus into RAM.
c)The virus makes copies of itself in RAM.
d)The mutation engine on the new viruses generates unique encryption routines that encrypt the virus body and mutation engine.
e)The new virus then looks for a host, infecting other files on disk.

Types of Viruses
1)Boot Viruses.
These viruses infect floppy disk boot records or master boot records in hard disk. True boot sector viruses infect only the DOS boot sector, while a subtype called MBR infects the master boot record.They replace the boot record program (which is responcible for loading O.S. in memory) copy it elsewhere on the disk or overwriting it. Boot viruses load into memory if computer tries to read from the disk while it is booting.
2)Program Viruses.
These infect executable program files, such as those with exetension like .EXE, .COM, .BIN, .SYS. These programs are loaded into memory during execution, taking the virus with them. Virus became active in the memory, making the copy of it-self and infecting files on disk.
3)Multipartite Viruses.
A hybride of Boot and Program Viruses. They infect program files and when infected program file is executed, these virus infect the Boot record. When you boot the computer next time the virus load into memory from Boot record and then starts infecting other program files on disk.
4)Stealth Viruses.
These virus use certain techniques to avoid detection.They may either redirect the disk head to read another sector insted of the one in which they reside or they may alter reading of infected file's size showen in the directory listing.
5)Polymorphics Viruses.
A virus that can encrypt its code in diffrent ways so that it appears diffrently in each infection. These virus are more difficult to detect.
6)Macro Viruses.
These viruses infect the macros within a document or template. When you open a word processor or spreadsheet document the macro virus is activated and it infects the Normal template. Since such viruses attach it self to document, if document is copied on another computer it infects that computer also.

You may have a Virus on your System if ...

Tips For Avoiding Virus Strikes

Myths about Viruses.

Virus Terminology