EXALT is a human paramilitary secret society who are a enemy faction that feature in XCOM: Enemy Within.
EXALT's aim is to take over the governments of the Earth and rule the world while everyone is distracted with the alien invasion. They want to evlove mankind by using the alien technology.
EXALT and Aliens
While not allied with the aliens they stay clear from them to try and conduct covert operations and propagnda missions to help them take over the world. They also use the alien technology to help them conduct research experiements.