On Aug. 15, more than 55,000 Saudi Aramco employees stayed home from work to prepare for one of Islam’s holiest nights of the year — Lailat al Qadr, or the Night of Power — celebrating the revelation of the Koran to Muhammad.

That morning, at 11:08, a person with privileged access to the Saudi state-owned oil company’s computers, unleashed a computer virus to initiate what is regarded as among the most destructive acts of computer sabotage on a company to date. The virus erased data on three-quarters of Aramco’s corporate PCs — documents, spreadsheets, e-mails, files — replacing all of it with an image of a burning American flag.