LPT Off Virus

Virus Name: LPT Off Aliases: V Status: Rare Discovered: February, 1993 Symptoms: .COM file growth; file date/time changes; interfers/disables printing Origin: USSR Eff Length: 256 Bytes Type Code: PRxCK - Parasitic Resident .COM Infector Detection Method: Sweep, AVTK, F-Prot, ViruScan, IBMAV, NAV, NAVDX, VAlert, PCScan, ChAV, Sweep/N, NShld, AVTK/N, NAV/N, NProt, IBMAV/N, Innoc, LProt Removal Instructions: Delete infected programs General Comments: The LPT Off virus was submitted in February, 1993, and is from the USSR. LPT Off is a memory resident infector of .COM programs, including COMMAND.COM. When the first LPT Off infected program is executed, the LPT Off virus will install itself memory resident in a "hole" in low, allocated system memory, hooking interrupts 17 and 21. Total system and available free memory, as indicated by the DOS CHKDSK program, will not be altered. Once the LPT Off virus is memory resident, it will infect .COM programs, other than very small .COM programs, when they are executed. Infected programs will have a file length increase of 256 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 infection occurred. The following text string can be found within the LPT Off viral code: "(c) 1992," LPT Off interfers with printing on the system printers by disabling the functionality of the 17h interrupt.