MX-335 Virus

Virus Name: MX-335 Aliases: V Status: Rare Discovery: June, 1993 Symptoms: .EXE file growth; file date/time changes; decrease in total system & available free memory Origin: Unknown Eff Length: 335 - 351 Bytes Type Code: PRhE - Parasitic Resident .EXE Infector Detection Method: F-Prot, AVTK, IBMAV, Sweep, ViruScan, NAV, NAVDX, VAlert, PCScan, ChAV, Sweep/N, AVTK/N, NShld, NAV/N, NProt, IBMAV/N, Innoc, LProt Removal Instructions: Delete infected files General Comments: The MX-335 virus was submitted in June, 1993. Its origin or point of isolation is unknown. MX-335 is a memory resident infector of .EXE programs. When the first MX-335 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 368 bytes. Interrupt 21 will be hooked by the virus in memory. Once the MX-335 virus is memory resident, it will infect .EXE programs when they they are executed. Infected programs will have a file length increase of 335 to 351 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 have been updated to the current system date and time when the infection occurred. The following text string can be found starting in the 19th byte of all infected files: "MX"