Sylwia Virus

Virus Name: Sylwia Aliases: V Status: New Discovered: January, 1995 Symptoms: .COM file growth; unexpected system reboots; decrease in available free memory (DOS 5.0) Origin: Unknown Eff Length: 734 Bytes Type Code: PRhCK - Parasitic Resident .COM Infector Detection Method: F-Prot, AVTK, IBMAV, Sweep, ViruScan, NAV, NAVDX, VAlert, PCScan, ChAV, AVTK/N, IBMAV/N, Sweep/N, NProt, NShld, NAV/N, LProt, Innoc 4.0+ Removal Instructions: Delete infected files General Comments: The Sylwia virus was received in January, 1995. Its origin or point of isolation is unkown. Sylwia is a memory resident infector of .COM files, including COMMAND.COM. Unexpected system reboots may occur when infected programs are executed. When the first Sylwia 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. Available free memory, as indicated by the DOS 5.0 CHKDSK program, will have decreased by approximated 1,008 bytes. Interrupt 21 will be hooked by the virus in memory. Once the Sylwia virus is memory resident, it will infect .COM programs when they are executed. Infected .COM programs will have a file length increase of 734 bytes with the virus being located at the end of the file. The program's date and time in the DOS disk directory listing will not be altered. The following text string is visible within the viral code in all Sylwia infected programs: "SYLWIA"