Computer Virus

Back to: COMPUTER SCIENCE SS1

 

Welcome to class!

In today’s class, we will be talking about computer virus. Enjoy the class!

Computer Virus

What are Computer Viruses?

Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation. A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

Computer viruses are often spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it’s from and you are expecting it.

A computer virus is a malware program that, when executed, replicates by inserting copies of itself (possibly modified) into other computer programs, data files, or the boot sector of the hard drive; when this replication succeeds, the affected areas are then said to be “infected”.

Viruses often perform some type of harmful activity on infected hosts, such as stealing hard disk space or CPU time, accessing private information, corrupting data, displaying political or humorous messages on the user’s screen, spamming their contacts, logging their keystrokes, or even rendering the computer useless.

Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files. Computer viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.

Types of viruses

There are different types of viruses:

1. Boot Sector Virus – targets the boot sector of a hard drive and crucially affects the boot process. Boot sector viruses became popular because of the use of floppy disks to boot a computer. The widespread usage of the Internet and the death of the floppy has made other means of virus transmission more effective.
2. File Infection Virus – coded viruses that attach themselves to .exe files; compressed files such as zip or drive files.
3. Multipartite Virus – cross between a file virus and a boot sector virus. These type of viruses spread in many different ways. Their actions vary depending on the OS installed and the presence of certain files. They tend to hide in the computer’s memory but do not infect the hard disk.
4. Network Virus – uniquely created to quickly spread throughout the local area network and generally across the Internet as well. Typically moves within shared resources like drives and folders.
5. Macro Virus – infects program files that use macros in the program itself, such as word processors. These viruses infect the files created using some applications or programs that contain macros such as doc, pps, xls and mdb. They automatically infect the files with macros and also templates and documents that are contained in the file. They hide in documents shared through e-mail and networks. Macro viruses include:
   • Relax
   • bablas
   • Melissa.A
   • 097M/Y2K
6. E-mail Virus – generally this is a macro virus which multiplies by sending itself to other contacts in your address book, in hopes they’ll activate the virus as well. This is a virus spread via an email. Such a virus will hide in an email and when the recipient opens the mail.

Evaluation

1. What are computer viruses?
2. List and explain the various types of computer viruses.

 

In our next class, we will be talking about Types of Computer Virus. We hope you enjoyed the class.

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