As the dust settles on yesterday evening's revelation that the U.S. government has been mining data from most of Silicon Valley's largest companies in a program called "PRISM," one question stands out: How did the NSA get access?

Apple, Google, Yahoo! and Microsoft, the largest companies involved in PRISM, the existence of which was revealed last night in a simultaneous Washington Post and Guardian scoop, have categorically denied knowledge of or participation in the program in a series of statements, while acknowledging that they do provide targeted access to the government when required to do so by law, generally according to court orders.

"We have never heard of PRISM," says Apple's spokesman. "If the government has a broader voluntary national security program to gather customer data we don't participate in it," says Microsoft's. "We do not provide the government with direct access to our servers, systems, or network," says Yahoo!'s. "Google does not have a 'back door' for the government to access private user data," says Google's.

Even unofficially, the tech companies seemed baffled by the allegations. The Guardian spoke with tech executives off the record, all of whom were "confused" by the documents published in the paper. None had ever heard of PRISM.

So what gives? Does the government have backdoor access so secret that not even their targets are aware? Are the tech companies lying? Or are they forbidden—as Verizon allegedly is with its NSA arrangement—from acknowledging its existence to an absurd extent?

[image via the White House Flickr]