This is an excellent thread on Reddit concerning this question. Redditor Rickmaz has this great answer:
retired Delta and ex-USAF pilot here. Civilian aircraft have no missile detection systems. It is unlikely but possible that they could have visually seen it coming at them (they look like an extremely high speed telephone pole coming at you). But most likely it approached the aircraft from the rear, unseen, after having either a radar lock on or IR lock on from engine heat. Even if you saw it visually, a civilian airliner is not really capable of evasive maneuvers that would successfully avoid a hit. Also, civilian airliners are not equipped with military anti-missile defenses: ability to deploy metallic chaff to confuse the incoming missile, or infrared flares to act as decoys to the missile.
It seems El Al, the Israeli carrier, is the only one that equips its aircrafts with missile countermeasures.