Computer Virus

                 

Virus
    
   - A Virus is a program that copies itself and infected a PC, spreading from one file to another, and then from one PC to another when the files are copied or shared. Viruses can be very destructive, causing loss of information

   -  Computer virus is a malicious program or code that gets copied or attached to other files in a computer without the knowledge of the user and as a result malfunctions the computer in one or the other way.Once a virus invades a system it copies itself and spreads from one file to another and then from one computer or network to another when the file are being copied or shared. The virus modified files and even the operating system itself. Viruses can be very destructive,causing loss of information.

   -    A computer Virus is a malicious software program designed to damage a computer or interfere with other programs and functions. 

   -    A virus is just a computer program.Like any other program,it contains instructions that tell your computer what to do.But unlike an application, a virus usually tells your computer to do something you don’t want it to do, and it can usually spread itself to other files on your computer and other people’s computer.

V - Vital

I  -  Information

R - Resource

U - Under

S - Siege



                                                      Do you know

The First PC Virus was a boot sector virus called (C)Brain,created in 1986 by the farooq Alvi Brothers,from pakistan.The creeper Virus written by Bob Thomas in 1971 was first detected on ARPANET,in the early 1970s.

The following are the important characteristics of a virus:

1. It is able to replicate.
2. It requires a host program as a career.
3. It is activated by external action.

4. Its replication ability is limited to the (virtual) system.

How do computer viruses spread? 

We have learnt that a computer virus is a piece of self-replicating code attached to some other pieces to code. Computer viruses move from computer to computer by attaching themselves to files or boot records of disks and diskettes. These days it is common to find viruses in e-mail attachments and other program that can be downloaded from the internet. Sometimes the virus code maybe harmless for example, it may display funny message for play a tune.But sometimes it may be very harmful and may proceed on to delete and modified files. Viruses can also spread via an infected pen drive ,CD, DVD or other storage media.

Types of Virus

- Boot Sector Virus

- Macro Virus

-  File Virus

- Network Virus

- Stealth Virus

- Space Filler Virus

- FAT Virus

- Worms

- Directory Virus

1. Boot Sector Virus
                  

This type of virus is attached the boot sector by attaching itself the DOS boot sector on floppy diskettes or the master board record on hard disks.So they are called as the boot record infector of system virus. Such virus are of the memory resident type.

1. Macro virus:-

• A macro virus is an instruction that carries out program commands automatically .

• Macro viruses are macros that self-replicate.

• These virus affects microsoft office application such as WORD and EXCEL.

• Examples:- Relax,MelissaA and Bablas etc.

2. File virus

• File virus attack and modify executable pr program file (having extension .com , . exe, . bat). Normal intelligence memory and slowly in infective other virus.

•  When one of these programs is run,directly or indirectly.

• There are large number of viruses which belongs to this category.

3. Stealth viruses:-

• It has ability to hide itself from some antivirus software programs.

• Some antivirus program can’t detect them.

4. E-mail :-

• It is a type of virus that spread easily through attachments to an e-mail messages or a downloaded file.
            

• These viruses can replicate itself by automatically mailing copies of itself to all the email ids present in the address book.

That is why it is important that you never open e-mail attachments unless you know the sender.

Effects of computer virus

• Corrupting files

• Formatting the hard disk, thus destroying date

• Slowing down the system

• Deleting the system files or renaming the system files makes the system hung.

Prevention of computer virus

• Install an antivirus software.

• Regularly update the program.

• Try to avoid downloading and installing software from the internet.

• Install only registered copies of software on the system.