Source: tygersthunder on Reddit

So myself and a friend did quite a bit of testing yesterday and found some VERY useful things. (Mind you that these quantities are only assigned values and not code)

  1. Zombies will NOT aggro on a player if they are prone. Including actively crawling, touching the zombie, and firing a bow.
  2. Zombies will not aggro on a prone player that shoots an adjacent zombie in the head with a bow.
  3. Zombies that are nearly hit or only injured will aggro. This becomes a big issue due to it being very challenging to kill the aggroed zombie without crouching.
  4. Important note Zombies will disregard almost all heat levels to attack "deer bladder". Sometimes even allowing you to stand next to one and loot bags! (Credit to "Zero")

I have found the best way to explain the aggro system is like this:

The devs have said there is a "Heat" aggro system. Lets just use that term. While crawling the player has a Lvl 1 heat. The player crouches. His heat level becomes higher, to a level 3. Zombies in a small radius now detect the player. the player tries to crouch-walk away and is now a level 4 heat Ect.

Determination of heat levels:

Level 1: Prone (Moving and still)
Level 2: Firing a bow while prone
Level 3: Crouching
Level 4: Crouch walking
Level 5: Standing
Level 6: Standing and moving
Level 7: Firing a gun
Level 8: Setting off explosives

What detects specific values of heat:

Level 1: Close proximity Wolves Close proximity Bears
Level 2: Zombies directly effected by your bow shot (near miss or injured)
Level 3: Zombies in a small proximity around the payer area
Level 4: Zombies in a Med proximity.
Level 5: Zombies in a large proximity.
Level 6: Zombies in a large proximity. (Mostly indistinguishable from 5)
Level 7+: Zombies reach Critical Mass at this point. The size of the Mob and the Actions taken to defend against the mob cause more zombies to be attracted and the mob either grows in mass or is sustained.

Mitigating heat- What we have found is that the way to combat the heat system with this many zombies is to always keep your heat in mind so that the amount of heat generated can be gradually reduced if it is brought to high. Some of you may ask, "HELP! I cant mitigate heat because I need to use a high heat creation method to temporarily escape/survive." The trick is to only use the high heat method until you can do multiple heat dropping techniques together to drastically reduce your heat.

For example: get distance- Ok heat drop Crouching - Ok heat drop getting distance and crouching- Big heat drop

What I have found to be effective is the following: Get as much distance as possible, Break line of sight, crouch, further break line of sight, prone, kill the last remaining aggroed stragglers with a bow. I have only accomplished a 100% heat reduction a couple times and it takes place in VERY specific circumstances. I had a massive horde chasing me. I entered a residential area and ran through a house. I exited the house and jumped a fence. I then ran into another house, crouched and closed the door. exited the back door of that house and crouch-walked through the backyard, a hole in the fence, across the next yard and into the house. I closed the door, proned and crawled out the front of the house.

The theory being: Sprinting= heat level 6 broke LOS= Heat level 5 (Lost some of the horde) Jumped fence= Heat level back to 6 but the AI caused the zoms to run AROUND the fence instead of over it creating alot of distance heat level approximately 5 Broke LOS again and crouched= heat level 3-4 more distance and more LOS breaking= heat 2-3 last LOS break and prone= heat level 1

Lastly, rules to remember. A Zom aggroed will not lose aggro without at least 1 of 4 things: breaking LOS, distance, distraction, or death (Yours or theirs). Animals will only lose aggro upon death (Yours or theirs). If all else fails. Log out. Insta-100%-aggro drop.

TL:DR Move slow to avoid aggro. Once you get it, act like you are running from a cop to lose it. Log out if necessary.

Edited to add deer bladder info.