A countermeasure is a system used to generally divert various incoming attacks ranging from heat seeking missiles to general small arms fire. Countermeasures can either be passive, providing constant protection or concealment, or active, directed against incoming projectiles by manual or automatic activation.
Technological Countermeasures used in the Battlefield series generally are used for diverting incoming projectiles with various systems including, IR flares, IR smoke, ECM jammer, and others. The way technological countermeasures work in the Battlefield series is generally by ejecting a type of "decoy" to throw the guided projectile off course by having it follow a new source such as flares presenting a higher heat source therefore making it the new target of a heat seeking missile. Countermeasures can also be used more strategically, such as covering an attack or retreat. However, countermeasures are highly situational and not always effective.
Many vehicles in Battlefield 2142 carry Active Defense System, which temporarily neutralizes incoming anti-vehicle projectiles, excluding the Orbital Strike and II-29 Motion Mine. EMP blasts can still disable vehicles even if they are using active defense; vehicles can still raise active defense while disabled.
Active Defense does not protect against gunfire—infantry can still be harmed by bullets passing through the defense matrix. Friendly vehicles can block shots from allies; for instance, a tank attempting to shoot between a friendly battlewalker's legs may have its shell stopped by the same walker's AD.
In the Singleplayer campaign of Battlefield 3, the player and enemy jets can use IR Flares during the course of the jet mission, "Going Hunting". On the Hard difficulty the enemy jets encountered will seemingly release an accurate stream of flares, thus preventing any missile from hitting the target.
Vehicle operators can choose from a wider variety of countermeasures: