Selectron is a dangerous memory resident parasitic virus. It hooks onto INT 21h and writes itself at the end of .COM or .EXE files that are executed or opened. They contain the text strings:
"Selectron.1112": (C) Selectronics Software "Selectron.1258": Digouter"01/15/88" (C) Selectronics Software "Selectron.1800": (C) Selectronics Software Virus has been disabled. Countdown to Extinction...
This virus has 3 versions:
Selectron.1112 hooks INT 8 and 9. On Sunday when Ctrl+Alt+Del keys are pressed, it manifests itself with the video and sound effects.
Selectron.1258 hooks INT 9, 10h and 1Ch. Under debugger is beeps with PC speaker and reboots the computer. When Ctrl+Alt+Del keys are pressed, it slowly turns the screen off by using VGA card features.
Selectron.1800 is the encrypted virus. On Friday, 13th or depending on the host file name the virus displays:
Countdown to Extinction...
And manifests itself with the sound and Grim Reaper walks across the screen.
During this process, the virus prevents the user from changing the date of the computer.