A two-day outage that left millions of Skype users unable to use the popular Internet telephone program was caused by an abnormally high number of user restarts after a routine software update, the company said Monday.
The worldwide outage, which began on Thursday and ended on Saturday, left millions of Skype users unable to log on to make phone calls or send instant messages.
Luxembourg-based Skype, part of online auction giant eBay Inc., has more than 220 million users, of which 5 million to 6 million users are online at any given time.
In an update to users on Skype's Heartbeat blog, employee Villu Arak said the disruption was not caused by hackers.
"The disruption was initiated by a massive restart of our users' computers across the globe within a very short timeframe as they re-booted after receiving a routine software update," he wrote in a message posted early Monday.
"The abnormally high number of restarts affected Skype's network resources. This caused a flood of log-in requests, which, combined with the lack of peer-to-peer network resources, prompted a chain reaction that had a critical impact," he said in the posting.
It was the first major outage for Skype since October 2005, when service was down only for a few hours. The company was founded in 2003 by Niklas Zennstrom and Janus Friis.
"This disruption was unprecedented in terms of its impact and scope," Arak wrote. "We would like to point out that very few technologies or communications networks today are guaranteed to operate without interruptions."
