Most of the world's Internet users lost access to YouTube for several hours Sunday after an attempt by Pakistan's government to block domestic access affected other countries.
The outage highlighted yet another of the Internet's vulnerabilities, coming less than a month after broken fiber-optic cables in the Mediterranean took Egypt off line and caused communications problems from the Middle East to India.
An Internet expert likened the cause of the outage to identity theft by a Pakistani telecommunications company, which accidentally started advertising itself as the fastest route to YouTube.
But instead of serving up videos of skateboarding dogs, it sent the Internet traffic into oblivion.
Pakistan Telecommunication Authority ordered 70 Internet service providers to block access Friday to the YouTube video-sharing site because it contained material that was perceived as anti-Islamic movies.
The authority did not specify what the offensive material was, but an official for the agency said the ban concerned a trailer for an upcoming film by Dutch lawmaker Geert Wilders, who has said he plans to release a movie portraying Islam as fascist and prone to inciting violence against women and homosexuals.
The censorship action was intended to cover only Pakistan, but extended to about two-thirds of the global Internet population, according to Renesys Corp., a Manchester, N.H., firm that keeps track of the pathways of the Internet for telecommunications companies and other clients.
The greatest effect was in Asia, were the outage lasted for up to two hours, Renesys said.
YouTube, a unit of Google Inc., confirmed the outage, saying it was caused by a network in Pakistan: "We are investigating and working with others in the Internet community to prevent this from happening again."
Two apparent errors allowed the outage to propagate beyond Pakistan, said Todd Underwood, vice president of Internet community services at Renesys.