Virus.DOS.Ha1.1383, also known as Ha!, is a memory resident parasitic encrypted virus on DOS.


When the virus is loaded into memory, it hooks INT 21h and writes itself into the end of the executables that are run.

The infection size varies in different files, it is in a range of 1,458 to 1,472 bytes.

Advanced details

The TSR memory usage of the virus is 1,456 bytes.

MD5 hash:



On every 8th day, it also hooks onto INT 16h (keyboard) and switches the symbol "!" and space key when they are typed.

On every 16th day, this virus hooks onto INT 9 (keyboard interrupt) and when CTRL-ALT-DEL is pressed, the virus displays an ASCII art shifting "ha!" plus a message:

☼☼☼☼                    ☼☼☼
 ►►►                   ►►►►►
 ◄◄◄                   ◄◄◄◄◄
 ↕↕↕  ↕↕↕    ↕↕↕↕↕     ↕↕↕↕↕
 ‼‼‼‼‼ ‼‼‼       ‼‼‼    ‼‼‼
 ¶¶¶   ¶¶¶   ¶¶¶¶¶¶¶     ¶ 
 §§§   §§§  §§§  §§§
 ▬▬▬   ▬▬▬  ▬▬▬  ▬▬▬    ▬▬▬  
↨↨↨↨   ↨↨↨   ↨↨↨↨ ↨↨↨   ↨↨↨

          version A

Other details

For any leap year, the virus skips February 29th and count the day as average year. Say simpler, for March 5th in any year, the virus activates with the big "ha!" payload, it does not activate on March 4th in leap year even it is another 16th day in a year.

The virus contains the internal text string:

ha! version A

Additionally, not to be confused with the Ha virus, which has 2 variants: Ha.311 and Ha.709, are simply file infector viruses, programs infected by them may fail to run and cause a system crash.




Ha1 virus review by Alles Sandro

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