Name: Billiard.265 Category: Viruses Description: Details Billiard.2658 It is not a dangerous memory resident partly encrypted parasitic virus. When an infected program is executed, the virus decrypts its encrypted block of code by using INT 1 (tracing) tricks, hooks INT 9 (keyboard) and stays memory resident. On INT 9 calls the virus releases INT 9 and hooks 2Fh. On INT 2Fh calls the virus releases INT 2Fh and hooks INT 9 (as a result at any moment the virus hooks either INT 9 or INT 2Fh). On INT 2Fh calls the virus also intercepts the INSTALLATION CHECK (AX=AE00h) command that is executed when a copy of COMMAND.COM processor is run, checks the command line, and if command line begins with "DIR" string the virus searches for .COM amd .EXE files and writes itself to the end of the file. While working DIR command the virus temporary hooks INT 21h and "decreases" the length of infected files when they are accessed by FindFirst/Next DOS functions. On 31st of months the virus manifests itself by a video effect - it runs the symbols on the screen like playing billiard.