WHAT IS A VIRUS ?

WHAT IS VIRUS ?

• A computer virus is a malicious program that can spread to other devices and infect them. Viruses can attach to other programs, replicate themselves, and modify other programs by inserting their code into them. 
• In computers virus is a program that replicates to another program, computer boot sector or document.
  
• Virus can be transmitted as attachments to an e-mail or downloaded file or be present on CD.

TYPES OF VIRUS

• FILE INFECTORS:
  o It infects program files.
  o Normally infect executable files such as .COM or .EXT files.
  o Some virus can infect any program when the program is requested for execution such as .SYS, .OVL, .PRG and .MNU files.
  o Many of this virus are memory resident.

• BOOT SECTOR VIRUS:
  o This virus infects executable code found in certain system areas on a disk.
  o They attached to the DOS boot sector or the master boot record on hard disks.
  o Boot sector virus attaches themselves to the boot record information andactivate when user attempt to start up form disk.
  o This virus are always memory resident.

• MULTI-PARTITE VIRUSES:
  o Known as polypartite.
  o They infect both boot records and program files.
  o This virus is difficult to repair.
  o If the boot area is cleaned, but the files are not than boot area infected again.
  

• MACRO VIRUSES:
  o These are the most common virus and they tend to do the least damage.
  o These types of virus infect data files such as it can infect your word document and insert unwanted words or phrases.
  o Ex. W97M, Melissa

PROTECTION FROM VIRUSES

• Install software from original write- protected disks.
• Use secure operating system like UNIX.
• Do not install pirated software.
• Scans files downloaded from the internet.
• Scan your system regularly if you continue using internet.
• Use good antivirus program to scan removable devices as well as system.
• Do not open attachments who contains an executable files.
  
• Do not open spam or junk mails