1024 SBC Virus
Virus Name: 1024 SBC
Aliases: Ontario II, SBC
V Status: Rare
Discovery: October, 1991
Symptoms: .COM & .EXE growth; intermittent printing problems;
decrease in total system and available free memory
Eff Length: 1,024 Bytes
Type Code: PRhAK - Parasitic Resident .COM & .EXE Infector
Detection Method: ViruScan, AVTK, F-Prot, Sweep, ChAV,
NAV, IBMAV, NAVDX, VAlert, PCScan,
NShld, Sweep/N, Innoc, NProt, AVTK/N, NAV/N, IBMAV/N,
Removal Instructions: Delete infected files
The 1024 SBC virus was submitted in October, 1991. Its origin and
point of original isolation is Canada. 1024 SBC is a stealth
virus which infects .COM and .EXE programs, including COMMAND.COM.
It is based on the Ontario virus.
The first time a program infected with 1024 SBC is executed, this
virus will install itself memory resident at the top of system
memory but below the 640K DOS boundary, hooking interrupt 21.
Total system and available free memory, as measured by the DOS
CHKDSK program, will have decreased by 3,072 bytes. Interrupt
12's return will not have been moved. At this time, the virus
will also infect COMMAND.COM if it was not previously infected.
Infected COMMAND.COM files will not have any file length increase
as the virus will have overwritten part of the 00h characters
located at the end of COMMAND.COM.
Once memory resident, 1024 SBC will infect .COM and .EXE programs
when they are executed or opened for any reason. Infected .COM
and .EXE programs will have a file length increase of 1,024 bytes,
though the file length increase will be hidden if the virus is
memory resident. The virus is located at the end of the infected
A symptom of a 1024 SBC infection is that the user may experience
intermittent printing problems with the system printer.
Unlike several other viruses which hide the file length increase,
the DOS CHKDSK program will not return file allocation errors on
infected programs when the virus is memory resident.
1024 SBC is an encrypted virus, and no text strings are visible in
the viral code in infected programs.
See: Ontario Ontario III