Virus.DOS.Phantom1

The Phantom1 virus infects .COM and .EXE files when they are run, and activates its payload after around 20 minutes of no keyboard activity, when it draws a skull and displays this message:

Congradulations!!! Your computer is now infected with a high performance
PHANTOM virus! Coming soon: next virii based on the _C00LEST_ mutation
engine all over the world: the Advanced Polymorphic Engine! Enjoy this
intro! (C) 1994 by Dark Prince.