Ghost

Ghost is a perk that featured in other CoD games, (MW2 as Cold-Blooded). It allows a player to be hidden in the radar to avoid been spotted by enemies. After the last update (14/10/12 patch), Ghost perk is unlocked at level 8.

Ghost Pro
It allows players to remain unspotted by UAVs, Radars or Sentry Guns. To get Ghost pro:
 * Destroy 10 enemy Aircraft.
 * Get 30 kills in one match using a Sniper Rifle.
 * Destroy 1 Sentry Gun while undetected.

Ghost Elite
In the Elite version Ghost players go completely invisible. As allows them to be undetectable by Thermal Scopes, and no red crosshair or name is shown when targeted. In addition, Gunships cannot spot them as no Red Square will appear. To get Ghost Elite:
 * Destroy 20 enemy Aircraft with any non-killstreak weapon. (RPGs, AT4, etc)
 * Get 25 headshots with a Sniper Rifle.
 * Get 100 kills with Ghost.
 * Destroy 5 Sentry Guns.

Curiosities

 * UWTF's Ghost Perk character model's face is modeled after Yevgeny Rodionov, a Russian young man soldier who was been beheaded by chechens during the First Chechen war. The character model is a tribute to him.