Cliff Saran’s FUD blog

Skype is now back online. But why did it fail? Villu Arak, writing on heatbeat.skype.com site stated:

The Skype peer-to-peer network became unstable and suffered a critical disruption. The disruption was triggered by a massive restart of our users’ computers across the globe within a very short timeframe as they re-booted after receiving a routine set of patches through Windows Update.

It looks like Microsoft's August 14th patch update may be the root cause for Skype spectacular crash. Skype user who downloaded the monthly MS patch had their PCs reboot as part of the update, causing them to restart and login to Skype. This led to a flood of log-in requests. According to Arak, combined with the lack of peer-to-peer network resources, this prompted a chain reaction that had a critical impact - in effect, it was a massive denial of service attack caused by Skype users all trying to login at the same time.

The key question is who is responsible. Should Microsoft be held accountable. Perhaps Windows Update could be reengineered to stagger updates? Maybe the users are at fault as they all tried logging in at the same time. Or Skype should have foreseen these circumstances and worked around such am occurrence.

What Skype's downtime does show is the fragility of modern IT systems to external factors.