It is not a dangerous memory resident parasitic virus. It hooks INT 21h and writes itself to the end of EXE files that are executed. In year 2000 the virus decrypts and displays the messages:
Wellcome to 21st century.
Author (Martin Zdila - MATOSoft) wish you no viruses in your computer
(except me - APOKALIPSA). I (virus) was born in SLOVAKIA in 1997/98.
Don't panic, I am harmless virus what is waiting for APOKALIPSA.
Press any key to continue.
Oh my God allAPOKALIPSA is here !!!
ALL DATA ON YOUR DISK ARE DESTROYED, FOREVER !
... ha ha ha. I got you! Great
joke, isn't it ?!
