These are dangerous nonmemory resident encrypted parasitic viruses. They search for COM files, then write themselves to the end of the file. Then the viruses delete the files by using the masks:
*._* *.ms
Depending on the system time the viruses display the messages and halt the computer. "Helga.666.a" displays the message in Russian. "Helga.666.b" displays:
WARNING: ALL DATA ON NON-REMOVABLE DISK
DRIVE C: WILL BE LOST!
Proced with Format (Y/N)?y
