Ah ( aka Tuesday and Jerusalem.Ah ) is a very buggy computer virus which infects COM files including command.com. Ah is based on the V1024 virus, and originated is Italy on May, 1991. 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. After it is memory resident, Ah 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. 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. 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. Aka can refer to the following meanings: Aka is an initialism for Also Known As. ... In computer security technology, a virus is a self-replicating program that spreads by inserting copies of itself into other executable code or documents (for a complete definition: see below). ... In MS-DOS and compatible DOSes, and in 8-bit CP/M, a COM file is a simple type of executable file with the file name extension (not to be confused with the . ... The title given to this article is incorrect due to technical limitations. ... Kilo (symbol: k) is a prefix in the SI system denoting 103 or 1,000. ... The acronym DOS stands for disk operating system, an operating system component for computers that provides the abstraction of a file system resident on hard disk or floppy disk secondary storage. ... A byte is commonly used as a unit of storage measurement in computers, regardless of the type of data being stored. ... In computer science, an interrupt is a signal from a device which typically results in a context switch: that is, the processor sets aside what its doing and does something else. ... For capital punishment by suspension from and breaking of the neck, see hanging. ... Typical hard drives of the mid-1990s. ...

The following text string is found in infected files: In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ...

• "(C) David Grant Virus Research 1991 PCVRF Disribuite this virus freely!!! ...ah...John...Fuck You!"

Ah is believed 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.

it is also a whale. A large, humpback whale.

External links

• Computer Viruses (A), by Probert Encyclopedia
• Ah virus, by McAfee