604 Virus

Virus Name: 604 Aliases: V Status: Rare Discovery: September, 1993 Symptoms: .COM file growth; decrease in total system & available free memory Origin: Unknown Eff Length: 604 Bytes Type Code: PRhCK - Parasitic Resident .COM Infector Detection Method: F-Prot, AVTK, IBMAV, Sweep, ViruScan, NAV, NAVDX, VAlert, PCScan, ChAV, NProt, Sweep/N, NShld, AVTK/N, IBMAV/N, Innoc, NAV/N Removal Instructions: Delete infected files General Comments: The 604 virus was submitted in September, 1993. Its origin or point of isolation is unknown. 604 is a memory resident infector of .COM programs, including COMMAND.COM. When the first 604 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 880 bytes. Interrupt 21 will be hooked by the virus in memory. Once the 604 virus is memory resident, it will infect .COM programs when they are executed. Infected programs will have a file length increase of 604 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. No text strings are visible within the viral code.