A few hours ago, Pakistan Telecom (AS 17557) began advertising a small part of YouTube's (AS 36561) assigned network. This story is almost as old as BGP. Old hands will recognize this as, fundamentally, the same problem as the infamous AS 7007 from 1997, a more recent ConEd mistake of early 2006 and even TTNet's Christmas Eve gift 2005.
Just before 18:48 UTC, Pakistan Telecom, in response to government order (thanks nsp-sec-d) to block access to YouTube (see news item) started advertising a route for 208.65.153.0/24 to its provider, PCCW (AS 3491). For those unfamiliar with BGP, this is a more specific route than the ones used by YouTube (208.65.152.0/22), and therefore most routers would choose to send traffic to Pakistan Telecom for this slice of YouTube's network.
I became interested in this immediately as I was concerned that I wouldn't be able to spend my evening watching imbecilic videos of cats doing foolish things (even for a cat). Then, I started to examine our mountains of BGP data and quickly noticed that the correct AS path ("Will the real YouTube please stand up?") was getting restored to most of our peers.
The data points identified below are culled from over 250 peering sessions with 170 unique ASNs. While it is hard to describe exactly how widely this hijacked prefix was seen, we estimate that it was seen by a bit more than two-thirds of the Internet.
This table shows the timing of the event and how quickly the route propagated (this is actually a fairly normal propagation pattern). The ASNs seeing the prefix were mostly transit ASNs below, so this means that these routes were distributed broadly across the Internet. Almost all of the default free zone (DFZ) carried the hijacked route at least briefly.
Yes, I made the lolcat image. It's the lamest thing I've ever done, yet I have no shame.
