Sneak

Sneak is a Fallout, Fallout 2, Fallout Tactics, and Fallout 3 skill.

Quiet movement, and the ability to remain unnoticed. If successful, you will be much harder to locate. You cannot run and sneak at the same time unless you have the Silent Running perk.

Fallout, Fallout 2 and Fallout Tactics
Initial Level: Starting Sneak skill is equal to 25%  (1% x Agility). Average characters will have a 30% Sneak.

Fallout 3
Unlike its predecessors, in Fallout 3 a player can both sneak and run at the same time regardless of perks, however, without the silent running perk the player will suffer a detection penalty while running.

The stealth state is displayed while crouching: Note: As soon as the conditions are satisfied for any state it replaces the one above it on the HUD even though the player may still be in the HIDDEN state to several targets around them.
 * [HIDDEN] means undetected by everyone.
 * [DETECTED] means detected by a friendly target or multiple friendly targets.
 * [CAUTION] means being searched for by an unfriendly target or multiple unfriendly targets.
 * [DANGER] means detected by an unfriendly target or multiple unfriendly targets.

Successful sneaking is dependant on many factors:
 * Sneak skill: The Sneak skill applies whenever the player crouches. The higher the player's Sneak skill, the easier it is to remain undetected while attacking, stealing, or picking someone’s pocket.
 * Cloaking Fields: The Stealth Boy will wrap the user in a cloaking field that makes them more difficult to detect while sneaking.
 * Enemy’s perception: Enemies with low perception are easier to sneak around than enemies with high perception.
 * Line of sight: While out of sight an enemy can only detect the player through sound.
 * Light level: The player is more difficult to see in dark areas or at night if outdoors. The Pip-Boy light, while active, will make the player much more visible.
 * Movement: The player is hardest to detect when motionless, easiest to detect when running.
 * Apparel weight: Heavier apparel makes more noise when moving.
 * Sound: Most melee weapons make very little noise; bigger guns make a lot of noise.

Attacking while undetected by the target results in an automatic “sneak” critical if the attack hits. It is possible to miss a sneak attack which will result in detection by the target. For best results, maximize chance to hit as much as possible before attacking so the sneak critical is not wasted. It is possible to get sneak critical while being detected by one target, friendly or unfriendly, on another target that has not detected the player.

It is possible to kill an enemy without alerting those around them if the "sneak" critical is also a one hit kill even with loud weapons like the Assault Rifle. Additional attacks after the first, queued in V.A.T.S., will be treated as non-sneak attacks and will reveal the player's location to the target and possibly other enemies, presumably because the target then alerts their friends.

If the player can close to melee range of an enemy while remaining undetected by the target they can then be pickpocketed and a live mine or grenade can be added to their inventory. The explosive will detonate after a short timer automatically killing the target regardless of the player's explosive skill or the target's health or resistances. The explosion can damage or even kill the player if they do not move out of the area or take cover quickly.

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