Goldbug was the famed computer virus that was grafted onto pirated copies of id Software's Doom II for MS-DOS 6.x in late 1994/early 1995. It could theoretically infect any computer running MS-DOS 6.x.

The virus would make quick work of any computer it infected. It would install itself while Doom II was installing and immediately move itself to the hard disk's boot sector, exploiting DOS's weak file permissions scheme. From there it would delete any running or idle antivirus software, delete any antivirus logfiles, and any antivirus checklist files it would find, and then it would clear the CMOS memory. The CMOS, of course, stores the motherboard's BIOS, and without the BIOS the operating system cannot load itself. This lead to just about every infected computer to instantly become a beeping, monitor-blinking mess, upon Doom II's successful installation, or before it, depending on the speed of the computer.

Due to the relative rarity of network connections and internet connections around that time, Goldbug kept itself to its host computer and did not propagate to other network computers or hubs.

The fix was one of hackerdom's most expensive -- a new motherboard and new hard drive for any computer unfortunate enough to become infected. Simply resetting the CMOS wouldn't work. If you were tech-savvy enough, you could've just repaced the EEPROM containing the BIOS and then get a new hard drive, but any way you look at it, the fix was not cheap, especially at mid-1990s computer hardware prices.