The National Security Agency (NSA) website went down on Friday at around 5:15 p.m., Eastern Time.
That hearsay comes largely from Twitter, where Anonymous-related accounts have posted messages, including, "So If it's a attack comming from me, or maybe from a country? won't say! It's just looks like a start of a cyber war," from @AnonymousOwn3r. Further tweets have encouraged the speculation, including, "Tango Down: http://nsa.gov by #Anonymous. Expect us October 25th, 2013 in your doorstep Obama," from @AnonOpsSE.
The NSA has been publicly chastised ever since whistleblower Edward Snowden blew the lid off its surveillance program. The NSA website is still down as of this story's posting.