Ninja

Ninja is a Tier 3 perk appearing in Call of Duty: Modern Warfare 2 and Call of Duty: Black Ops.

Call of Duty: Modern Warfare 2
Ninja stops users from appearing on Heartbeat Sensor attachments. It is unlocked at Rank 29.

The Pro version of this perk is unlocked after players kill 50 players in "close-quarters" while using the perk, and it reduces the movement noise volume (footsteps, mantling and climbing) by 75%, effectively replacing Dead Silence. The actual distance that constitutes "close-quarters" needed for the challenge is unknown (50 close-quarters kills will unlock the Pro version), but it is approximately the range at which the Tier 3 Perk Scrambler completely Scrambles the radar of enemies - Scrambler Pro is unlocked similarly by making "close-quarters" kills. It also may be the distance at which a Heartbeat Sensor can detect players.

This is useful to players who like going lone-wolf and sneak behind enemy lines. A complete custom stealth class often comprises silenced weapons, Cold-Blooded as their Tier 2 Perk, and Ninja Pro (silent footsteps are needed) as their Tier 3 Perk. As mentioned in Dead Silence, though it removes all "high-profile" movement (sprinting, climbing onto an obstacle/platform) noise, a player can imitate this quiet manner by moving while crouched or in ADS (aiming down the sight).

Ninja is most useful in games such as Sabotage and Search and Destroy as players with Heartbeat Sensors often wait by the objectives (or people using headsets), but it is often useless in other game types due to the rarity use of Heartbeat Sensors. Earlier in Modern Warfare 2's multiplayer there were more Heartbeat Sensors used as players were trying out attachments, so the Ninja perk was more useful.

Ninja Pro is more often used in all custom classes by players that use gaming headsets, which help them to hear other player's movements without theirs disrupting them. This has also stopped some players from Prestiging as they find it difficult to play the game without their footsteps being silent.

Call of Duty: Black Ops
Ninja returns as a Tier 3 perk in Black Ops. It is roughly equivalent to the Dead Silence perk from past Call of Duty games and shares effects with SitRep Pro in Modern Warfare 2.

Overview
Ninja reduces all player noise by 75%. Its pro version completely silences the player and doubles the volume of enemy sounds. Teammates without Ninja will be heard normally by the player.

Unlike in past Call of Duty games, Ninja Pro is not limited to footsteps alone. Ninja Pro silences falling, mantling, weapon switches, equipment deployment, and more. It also more than doubles the sound of enemy footsteps, as well as amplifying enemy callouts, reloading, and equipment deployment. It is useful to know the language of your team to distinguish friend from foe.

The November 18th patch balances audio levels making player noises much easier to detect. This makes Ninja and Ninja Pro much more useful. However, even with Ninja Pro, enemies do not make nearly as much movement noise as they do in Call of Duty: Modern Warfare 2. The volume of footsteps varies widely depending on the ground surface; on some surfaces footsteps are nearly silent. Additionally, while sprinting on some surfaces footsteps seem to make noise only every third or fourth step, again minimizing the usefulness of this perk.

Ninja Pro seems to let you pick up on enemy footsteps from slightly further away but not necessarily louder. Having a line of sight definitely lets you hear the footsteps easier than if you are around a corner.

Even with Ninja Pro, players will hear themselves mantling. This may be a bug and it's unclear if enemies can also hear the noise.

The 1.04 patch further adjusts Ninja Pro: "Additional sound mix tuning for Ninja Pro users – increased ranges and volume of enemy footsteps, and removed player footstep sounds on concrete material types."

Pro Challenges

 * Silenced Kills – Get 150 kills using the Suppressor attachment.
 * Back Stabs – Get 5 Backstabber Medals.
 * Plants – Plant the bomb 10 times in Demolition, Sabotage, or Search & Destroy.

Call of Duty: Modern Warfare 2
Even with Ninja Pro, players will still make a loud crunching sound when falling from an elevated height, just like its predecessor Dead Silence. Players with Ninja Pro will also make noise if they move through branches or bushes.
 * Ninja Pro actually reduces footstep sounds to a quarter of their original volume, but this is still extremely quiet and will almost never be heard.
 * SitRep Pro has no effect on Ninja Pro. Players using SitRep Pro will not be able to hear Ninja Pro users more easily than players who are not using SitRep Pro.
 * Friendlies using Ninja do not appear on Heartbeat Sensors.
 * Dead Silence was originally going to be an ability of one of the four planned multiplayer character abilities. However, the character models were scrapped and it was added as the Pro ability of Ninja.
 * The icon of this perk possibly made on early stage of development - it has the same style and dimensions as Call of Duty 4: Modern Warfare perks icons.

Call of Duty: Black Ops

 * The achievement, "Stand Down", uses the same Ninja logo.
 * The last challenge for getting Ninja Pro, which is planting 10 bombs, is different in Combat Training, since the player cannot play bomb related gametypes, such as Search and Destroy and Demolition.
 * The Backstabber challenge can be tricky with a simple melee and oftentimes the player will not get credit for a Backstabber medal after completing a melee from behind. A good way to ensure a Backstabber medal is to melee while using the ballistic knife. This will ensure a direct stab to the back.
 * Ninja Pro in Call of Duty: Black Ops is the first perk to be cancelled out by itself, instead of by another perk.