These are dangerous not memory resident encrypted viruses. They search for .EXE-files and write themselves to their ends. The viruses delete the files, they contain the text string:
*.eXe dOs ChKdSk.exE XcOPy.eXE MeM.ExE cHkLiS*.*
Depending of the system date and their internal counters the viruses display the messages and halt the computer:
IT'S WITCHING HOURall YOUR COMPUTER IS BEING HAUNTED ! HAHAHA...
Bad luck... You've got a virus in your system !
Think about using a virus-scanner which is more up-to-date !
Here lies a program in its coffin, executed by a user one time too often...
