Class 7

The first note covers Viruses in brief.

The full form of VIRUS is Vital Information Resources Under Seize. The essential resources of the computer like memory, processing speed, data and programs etc. cannot have normal operations when virus is spread. Virus programs are self – replicating and are continuously expanding their reach by infecting more and more computer file, resulting in loss of speed and destruction of data.

Virus programs make computer do things which you do not want. Normally, it enters through an infected floppy or Internet/E-mail.

TROJAN HORSE are simple programs that pretend to be useful applications  while they always do something destructive. They are not self replicating. A Trojan can spread only when it is copied to another system. The name Trojan Horse came from the wooden horse used by the Greek Army to conquer the city of Troy.

WORM is a special type of virus that can replicate itself and use memory, but cannot add itself to other programs.

MALWARE is made up of two words malicious and software. It is a software that enters into a computer and damages it without the knowledge of the user. Malware is a trouble causing program. It may be a virus, worm, Trojan horse or spyware. Malwares not only interrupt the normal working of a computer but also steal important information.

SPYWARE is a type of malware that is installed on computers and collects information about users without their knowledge. Spyware programs can collect various types of personal information about users and transmit them to someone else. These information can include internet surfing habits, visited web pages etc.


BOOT VIRUS: These infect the boot record and master boot records. Examples are Disk killer, Stone virus etc.

PRGRAM FILE VIRUS: These infect executable files, programs with extensions .exe, .sys, .drv etc.


  • Decreasing the speed of the computer by decreasing the memory
  • Causing strange movements on the screen
  • Displaying unusual messages
  • Unusual increase in disk space
  • Frequent systems hang
  • Showing abnormal write protect error
  • Reformatting the hard disk
  • Deleting or damaging files


  • Every PC should be equipped with some anti-virus program.
  • Always scan the pen drive before copying files.
  • Do not install pirated software.
  • Scan the hard disk twice a month.
  • Take the back up of important files everyday.
  • Use internet and e-mail attachments very carefully.



Antivirus softwares are computer programs which are designed to identify, prevent and remove virus from our computer. But installing it does not guarantee protection. We should keep on updating the latest version of Antivirus programs. Some of the popular antivirus softwares are Norton Antivirus, McAfee Virus Scan, AVG Antivirus etc.