Cold-Blooded

Cold-blooded is a Tier 2 perk appearing on Call of Duty: Modern Warfare 2 that makes players undetectable to all killstreak rewards and thermal imaging. Players using Cold-Blooded will be invisible to the UAVs, Sentry Guns, Harriers and computer controlled Helicopters and simply will not be targeted. With Predator Missile Strikes, AC-130 and Chopper Gunners, players using this perk will still appear on the screen but they will not be highlighted by a red square. Thus, the best strategy during one of these kill streak attacks is to simply stop moving as the black and white resolution for such attacks is poor and moving objects are much easier to see. Viewed through thermal scopes instead of appearing bright white, Cold-Blooded players will appear as shades of gray similar to the environment, However this may cause the player a disadvantage on snow maps, as the gray has more contrast with the environment, whereas the white-hot non-cold blooded players are much harder to spot against the white snow. As they are not truly invisible, moving Cold-Blooded players are much easier to spot through thermal scopes than stationary ones.

The Pro version prevents the red name and crosshairs from appearing on an enemy's screen when they are looking at the user. It is unlocked by destroying forty enemy killstreak rewards (of any kind, even UAVs) while using this perk. If a silencer is added this is very helpful to sniper classes (though damage is reduced). Just as in the original Modern Warfare in which silencers and the UAV Jammer perk were mixed.

Trivia

 * The perk picture shows a lizard (a "cold-blooded" reptile) surrounded by snowflakes.
 * The perk picture can also be considered a chameleon as the player tends to blend in with the surrounding environment.
 * In reality, "Cold-Blooded" refers to an organism that cannot produce its own heat, referring to the fact that most of the weapons this perk blocks use body heat as a means of targeting.
 * There are three ways of obtaining the pro version of this perk: shoot down enemy air support with a launcher, steal enemy care packages, or destroy enemy sentry guns.
 * With this perk it is not safe to stand next to someone without it during an enemy killstreak. They will be targeted and you may be killed with them when they are hit. However, in friendly fire games, you will be safer, as the average player will not attack players without red boxes since they will assume that you are friendly.
 * Because of this, players trying to shoot down enemy aircraft with cold blooded should stand away fron team-mates.