Countermeasures

Countermeasures are anti-missile and sensor interference systems available onboard ships and some vehicles.

Countermeasures consist of two main types:

"A 'decoy' is an object that effectively creates a powerful signal source that missiles are attracted to. In Alpha 3.11, all missile types will react to decoys to varying degrees. Of course, a decoy has a limited time in which it is active. Once a decoy is burned out, an incoming missile will try to regain a lock on to its original target."
 * Decoys (sometimes referred to as "flares"): point-like diversionary countermeasuresCountermeasures - Decoys.jpg

"A 'noise field' creates a small space in which signatures are actively distorted and jammed. A ship deploying a noise field fires a small projectile that explodes and spreads out tiny particles that confuse sensors, regardless of whether they're based on EM, IR, or CS signatures. If the ship's signature is low enough, a pilot can even hide in that cloud. However, this will also actively jam the ship sensors as well, so radar contacts will disappear. Missiles are affected by this in the same way, of course."
 * Noise (sometimes referred to as "chaff"): field-effect sensor interference countermeasuresCountermeasures - Noise.jpg

As of Alpha 3.11, both countermeasures types are effective against all missile guidance types and sensors (electromagnetic, infrared, and cross-section) to varying degrees.