These are harmless memory resident parasitic viruses. They hook INT 21h, and write themselves to the end of EXE files that are executed. The header of infected files contains the word:
AJ
"AJ.793" is a very dangerous virus. In February, starting from the 6th, it formats hard drive sectors. It also corrupts the anti-virus databases of ANTI-VIR.DAT and CHKLIST.MS.
