April 26, 1999
The first known virus to target the flash BIOS of a PC, the CIH/Chernobyl Virus triggers its payload on this day, erasing hard drives and disabling PCs primarily in Asia and Europe. One of the most destructive viruses in history, it is estimated that 60 billion PCs were infected worldwide causing $1 Billion in damages.
The virus had been created exactly one year earlier on April 26, 1998 by Taiwanese student Chen Ing-hau and set to trigger its destructive payload exactly one year later. It began to spread in the wild and was first discovered in June of 1998, given the name CIH due to the author’s initials discovered in the virus code. From this time forward it was reported that a variety of companies accidentally distributed the virus through various downloads, updates, and CDs. When the virus triggered on this date it just happened to coincide with the date of the Chernobyl disaster in 1986 and therefore the press began to call it the Chernobyl virus, even though there has never been any evidence to show that this date was chosen intentionally for this reason.