It appears that Reddit has been the recipient of a National Security Letter, after the warrant canary it has published in its annual transparency reports has disappeared.

A warrant canary is a technique whereby companies can get around the restrictions involved with National Security Letters, which typically bar the recipient from letting on that Uncle Sam is snooping around on their servers. Companies can, however, say that they haven't received one, and then take that comment down once the Feds come knocking.

Reddit had a canary up last year, but on Thursday the site released its 2015 transparency report and it was quickly spotted that the canary had taken wing and was no longer mentioned. Reddit being Reddit, plenty of angry words were posted online and then the user /spez – aka the site's CEO Steve Huffman – came on to comment.

"I've been advised not to say anything one way or the other," he said, which makes things clear.

So it now seems as though the NSA, FBI, or other unknown agencies have been tapping into Reddit's servers to gather information on its users. Because of the restrictions involved, we won't know quite what has happened, but it could be anything from a one-off investigation all the way through to Reddit's servers now being a part of the NSA's PRISM monitoring scheme.

Because of the highly secretive nature of National Security Letters, the targets of investigation also can't be informed. You'd hope the data request was made for legitimate reasons, not just to scope out who has a plushie fetish. But we'll probably never know. ®