This is a benign memory resident parasitic encrypted stealth virus. It searches for original address of INT 21h handler in DOS area, hooks INT 21h and writes itself to the end of the files. This virus uses a method of MCBs correction and KEEP DOS function.
This virus infects COM and EXE files that are executed. While infecting they rename the file to "RUBBIT.$$$", infect it and then rename back to original name.
On September, 9th the virus displays the message:
## !! RuBBit Version 2.1 !! ##
## << How do you do >> ##
## !! Today is My Birthday !! ##
$$ OH! YES! Happy Birthday To You ! $$
This virus also contains the texts:
RuBBit
