Outbreak of CIH computer virus.

CIH, also known as the Chernobyl virus, is a computer virus that targets computers running the Windows 9x family of operating systems. There are several variants, with different trigger dates that cause the virus to activate on different days, ranging from once a month to once a year. The most widespread variant first activated on April 26, 1999, causing widespread damage to hundreds of thousands of computers worldwide and resulting in hundreds of millions of dollars of losses. CIH is notorious for its destructive payload, which overwrites critical areas of a computer's hard drive, leaving the data inaccessible. On some systems, it also intentionally corrupts the system's flash BIOS firmware stored on the motherboard. This makes the computer unable to boot, leaving the computer unusable until the BIOS chip or the entire motherboard is replaced.