Drop Virus

Virus Name: Drop Aliases: V Status: Rare Discovered: October, 1992 Symptoms: .COM & .EXE growth; decrease in total system & available free memory; file date/time changes Origin: USSR Eff Length: 1,131 - 1,163 Bytes Type Code: PRhAK - Parasitic Resident .COM & .EXE Infector Detection Method: AVTK, Sweep, F-Prot, ViruScan, IBMAV, NAV, NAVDX, VAlert, PCScan, ChAV, Sweep/N, NShld, Innoc, NProt, AVTK/N, NAV/N, IBMAV/N, LProt Removal Instructions: Delete infected files General Comments: The Drop virus was submitted in October, 1992. It is from the USSR. Drop is a memory resident infector of .COM and .EXE programs, including COMMAND.COM. The first time a program infected with the Drop virus is executed, Drop will install itself memory resident at the top of system memory but below the 640K DOS boundary. Total system and available free memory, as indicated by the DOS CHKDSK program, will have decreased by 3,600 bytes. Interrupt 21 will be hooked by the virus in memory. Once the Drop virus is memory resident, it will infect .COM and .EXE programs when they are executed or opened for any reason. Infected .COM programs will have a file length increase of 1,131 bytes. Infected .EXE programs will have a file length increase of 1,153 to 1,163 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 have been updated to the current system date and time when infection occurred. No text strings are visible within the viral code in infected programs. It is unknown what Drop may do besides replicate.