There have been a few hypotheses on these FRBs. It seems pretty clear that they are not natural in origin based on the signature they leave. Others speculated that they were long range communication beacons.
http://www.space.com/35996-fast-radio-bursts-powering-alien-spacecraft.html
http://www.space.com/35996-fast-radio-bursts-powering-alien-spacecraft.html