Survivors repairing or healing within your Terror Radius suffer from the following effects:

Increases the Trigger odds of Skill Check by 10 percent.
Decreases the Success zone of Skill Checks by 40/50/60 percent.

Grants the Undetectable status effect after gaining Bloodlust Tier 1.  The status effect is removed once you lose Bloodlust.

Gain 50percent more Bloodpoints for actions in the Hunter Category.

After unhooking a survivor, all survivors who are at least 60/50/40 meters away from that hook have their Aura revealed to you for 4 seconds.

The Auras of regressing Generators are highlighted in white.

If the Regression progress is interrupted on a Generator, its Aura will be highlighted in yellow for 8/12/16 seconds.
Surveillance increases the audible range of Survivors Generator-repairing noises by 8 meters.