Mr_Gu Virus
Virus Name: Mr_Gu
Aliases: Mr_Gu.545
V Status: New
Discovered: July, 1995
Symptoms: .COM file growth;
decrease in available free memory
Origin: Unknown
Eff Length: 545 Bytes
Type Code: PRhCK - Parasitic Resident .COM Infector
Detection Method: NAV, NAVDX, IBMAV, VAlert, AVTK, ViruScan, ChAV,
F-Prot, PCScan,
NAV/N, IBMAV/N, AVTK/N, NProt, NShld, Innoc
Removal Instructions: Delete infected files
General Comments:
The Mr_Gu virus was received in July, 1995. Its origin or point
of isolation is unknown. Mr_Gu is a memory resident infector of
.COM files, including COMMAND.COM.
When the first Mr_Gu infected program is executed, this virus will
install itself memory resident at the top of system memory but below
the 640K DOS boundary, not moving interrupt 12's return. Available
free memory, as indicated by the DOS CHKDSK program from DOS 5.0,
will have decreased by 1,616 bytes. Interrupt 21 will be hooked by
the virus in memory.
Once the Mr_Gu virus is memory resident, this virus will infect all
of the .COM files in the current directory when a DOS COPY command
is executed. Infected files will have a file length increase of
545 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 not
be altered. The following text strings are visible within the viral
code:
"*.com"
"Mr.Gu"
Known variant(s) of Mr_Gu are:
Mr_Gu.635: Received in January, 1996, this is a 635 byte version
of the Mr_Gu virus described above. Its size in memory is also
1,616 bytes, hooking interrupt 21. It infects .COM files, but
not COMMAND.COM, when they are executed, opened, or copied.
Infected files will have a file length increase of 635 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 not be
altered. The following text strings are encrypted within the
viral code:
"*.com"
"COMMAND.COM"
"Mr.Gu"
Origin: Unknown January, 1996.