Kevin Poulsen at Wired has been trying to find out what happened to the Department of Homeland Security system that screens incoming visitors to the US:
The August computer failure led to long queues at airports across the country, but was only tersely explained to the public. The DHS initially said a computer virus had infected one of the mainframe servers — in Virginia. Later, the agency reversed itself and claimed there was no virus, and the outage was a normal computer crash.
They filed a Freedom of Information Act and got some runaround, but finally got the answers: It was apparently a virus.