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Ada (computer virus)

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Ada is a memory resident, file infecting computer virus which infects COM files, including command.com. It was first discovered in Argentina in October, 1991. Upon infection, Ada becomes memory resident as a low system memory TSR. Once it is memory resident, Ada infects .COM files as they are executed, such as command.com. Programs infected with Ada will have a file size increase of 2,600 bytes with the virus being located at the beginning of infected files. An infected file's date and time in the DOS disk directory listing are not altered. Available system memory as measured by the DOS CHKDSK program will have decreased by 21,296 to 21,312 bytes. Interrupts 08, 13, and 21 are hooked by the virus. Systems infected with Ada experience a slow clicking sound being emitted from the system speaker. This clicking will occasionally change in pitch. False and random "disk full" messages may also appear.

The following text strings are found in infected files:

  • "COMMAND.COM"
  • "PCCILLIN.COM"
  • "PCCILLIN.IMG"
  • "HATI-HATI !! ADA VIRUS DISINI !!Delete"

Ada specifically attacks the PC-cillin antivirus package, deleting PC-cillin if it is found.

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