Virus Name: Drop
V Status: Rare
Discovered: October, 1992
Symptoms: .COM & .EXE growth; decrease in total system & available free
memory; file date/time changes
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,
Removal Instructions: Delete infected files
The Drop virus was submitted in October, 1992. It is from the USSR.
Drop is a memory resident infector of .COM and .EXE programs,
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.