Willistrover III Virus

Virus Name: Willistrover III Aliases: V Status: New Discovered: August, 1993 Symptoms: .COM & .EXE growth; unexpected system reboots; decrease in total system & available free memory; "Not ready error reading drive" error messages Origin: Bolivia Eff Length: 965 - 979 Bytes Type Code: PRhAK - Parasitic Resident .COM & .EXE Infector Detection Method: IBMAV, Sweep, F-Prot, ViruScan, VAlert, PCScan, NAV, NAVDX, ChAV, AVTK 7.68+, Sweep/N, NShld, IBMAV/N, Innoc, NAV/N, LProt, AVTK/N 7.68+ Removal Instructions: Delete infected files General Comments: The Willistrover III virus was submitted in August, 1993, and is from Bolivia. It is a memory resident infector of .COM and .EXE programs, including COMMAND.COM. When the first Willistrover III infected program is executed, this virus will install itself memory resident at the top of system memory but below the 640K DOS boundary, not moving interrupt 12's return. Total system and available free memory, as indicated by the DOS CHKDSK program, will have decreased by 1,040 bytes. Interrupt 21 will be hooked by Willistrover III in memory. Once the Willistrover III virus is memory resident, it will infect .COM and .EXE programs when they are executed. Infected .COM files will have a file length increase of 965 bytes. Infected .EXE files will have a file length increase of 965 to 979 bytes. In both cases the virus will be located at the end of the file. The program's date and time in the DOS disk directory listing will not be altered. No text strings are visible within the viral code in Willistrover III infected programs. After all of the .COM and .EXE programs in the current directory have become infected, execution of the next infected program will result in the virus infecting the copy of COMMAND.COM pointed to by the COMSPEC environment parameter. At this point, a system reboot may occur, or the following message may be displayed requiring an appropriate action by the system user: "Not read error reading drive X Insert disk with \COMMAND.COM in drive X and strike any key when ready" The X in the above message will be the current drive letter. After COMMAND.COM is infected, unexpected system reboots may occur any time a program is executed.