Virus Name: Ah
Aliases: Tuesday, David-1173
V Status: Research
Discovery: May, 1991
Symptoms: .COM file growth; decrease in total system & available free
memory; system hangs; hard disk format; message
Eff Length: 1,173 Bytes
Type Code: PRhC - Parasitic Resident .COM Infector
Detection Method: ViruScan, F-Prot, Sweep, AVTK, NAV, NAVDX, IBMAV,
VAlert, PCScan, ChAV,
NShld, LProt, Sweep/N, Innoc, NProt, AVTK/N,
Removal Instructions: Delete infected files
The Ah, or Tuesday, Virus was received in May, 1991. Ah is based on
the V1024 virus, its origin is Italy. Ah is a very buggy virus
which infects .COM programs.
When the first program infected with Ah is executed, Ah 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 decrease by 1,216 bytes.
Interrupts 08 and 21 will be hooked by the virus.
After Ah is memory resident, it will infect .COM programs over 1K
in length when they are executed. Infected programs will increase
in size by 1,173 bytes, though the file length increase will be
hidden if Ah is resident. Their date and time in the DOS directory
will appear to be unaltered, though if the program's original time
was 12:00a, it will now be blank. The virus will be located at the
beginning of infected programs.
Systems infected with Ah will experience frequent system hangs.
These hangs occur when the user attempts to execute a .COM program
which is infected with Ah. They may also occur when the virus
attempts to infect an uninfected program. System hangs occur so
frequently with Ah that the virus is very noticeable.
The Ah virus activates on Tuesdays, at which time it will attempt
to format the first few tracks of the system hard disk.
Programs infected with Ah can be easily identified as they will
contain the following text strings:
"(C) David Grant Virus Research 1991 PCVRF
Disribuite this virus freely!!!
Ah is believe to have been created by the same person as several
other viruses from Italy, including Smack and Enigma. David Grant
and the PCVRF had nothing to do with its creation.
Known variant(s) of Ah are:
Ah-B: Similar to the original virus, this variant will
occassionally infect an .EXE program. It contains the same
text strings as the original virus.
Origin: Unknown October, 1992.
See: Alfa V1024