This is a dangerous, memory-resident parasitic virus. It hooks INT 9 and 21h, and sets INT 1 and 3 to HOLD RESET address, and writes itself to the end of the COM files that are executed or loaded into the memory for debugging or as overlays.
While creating a TSR copy, this virus do not modify the MCB chain, and may
halt the system. When the INT 9 is called (keyboard), the virus may change