These are dangerous memory resident encrypted parasitic viruses. They hook INT 21h and write themselves to the end of COM files that are executed.
Muny.969
After infecting 33 files the virus displays a message in Russian, then creates a new file with the name of currently executed file and with extension '.$'.
Muny.1870
The virus encrypts 256 bytes in the header of affected files. After infecting 50 files the virus calls its trojan routine that corrupts files and displays messages in Russian.
