Virus Name: Bubonic
V Status: Rare
Discovery: May, 1993
Symptoms: .COM & .EXE growth; DOS CHKDSK file allocation errors;
decrease in total system & available free memory;
sluggish DOS DIR commands
Eff Length: 2,181 - 2,193 Bytes
Type Code: PRhAK - Parasitic Resident .COM & .EXE Infector
Detection Method: ViruScan, F-Prot, Sweep, AVTK, NAVDX,
VAlert, NAV, IBMAV, PCScan, ChAV,
NShld, NProt, Sweep/N, AVTK/N, Innoc, NAV/N, IBMAV/N
Removal Instructions: Delete infected files
The Bubonic virus was received in May, 1993. Its origin or point of
isolation is unknown. Bubonic is a memory resident, fast infecting
virus which infects .COM and .EXE programs, including COMMAND.COM.
It is a size stealthing virus, hiding the file length increase on
infected files when they virus is memory resident.
When the first Bubonic infected program is executed, the Bubonic
virus will install itself memory resident at the top of system
memory but below the 640K DOS boundary, hooking interrupt 6B. Total
system and available free memory, as indicated by the DOS CHKDSK
program, will have decreased by 2,592 bytes. Interrupt 12's return
will not be moved.
Once memory resident, the Bubonic virus will infect .COM and .EXE
programs, including COMMAND.COM, when they are executed. Infected
.COM programs will have a file length increase of 2,181 bytes.
.EXE programs infected with Bubonic will have a file length increase
of 2,181 to 2,193 bytes, though occassionally one may increase in
size by up to 2,254 bytes. In both cases, the file length increase
is hidden when the virus is memory resident, and the virus is
located at the end of the file. The program's date and time in the
DOS disk directory listing will not be altered. The following text
strings are visible within the viral code in all Bubonic infected
Systems infected with the Bubonic virus will experience sluggish
DOS DIR command output. The DOS CHKDSK program, when executed with
the Bubonic virus in memory, will detect file allocation errors on
all infected files.