Effects of Viruses

The effect of a virus can sometimes be very destructive, involving large amounts of data. Different viruses have different effects. Some of these effects are listed below:

  • Corrupting files
  • Increasing file sizes
  • Interference with the display on the VDU
  • Formatting the hard disk, thus destroying data
  • Marking good sectors as bad
  • Destroying contents of some sectors at random
  • Slowing down the system
  • Scrambling file names by manipulating the directory contents; the data is all there, but the user is unable to access it
  • Changing all filenames to a single name.

Viruses are triggered off in various ways. For example, some viruses are triggered off by the date, such as the Jerusalem-B virus which waits for Friday the 13th, when it deletes the program files you execute without your permission. Other viruses are triggered by booting a system, such as the PC Stone virus, that occasionally displays the message 'Your PC is now STONED!' as your computer starts, and causes data loss on, both, the hard disk and floppy disks. The Raindrop virus waits till a .COM file is executed and then starts pushing the characters to the bottom of your screen. Hence, no proper display is possible till the virus is eradicated.