There has recently been some speculation on the identity of the Russia satellite Kosmos 2499. After being launched with a couple other Russian communications satellites, it was originally classified as debris, before it began making orbital maneuvers in an (apparently) purposefuly manner.
http://www.russianspaceweb.com/Cosmos-2499.html - more info
I personally don't think it's an ASAT system. If you want to kill a satellite in LEO, the method the Chinese used back in '07 is more than good enough. I'd guess it's some sort of intelligence satellite, intended to rendezvous with and get intel on other satellites. Not entirely unlike Prowler or Misty.