What backdoor protection is
Backdoor protection is a rule that stops you from taking down buildings without a creep escort. If there's no attacking-team wave nearby, the structure regenerates health and takes less damage.
- The goal. To forbid quietly razing a base by bypassing the lanes.
- The condition. No attacking creeps nearby → protection on.
- The effect. Fast regen + heavy damage reduction on the building.
Want to take a tower — bring creeps. Without a wave, a protected building heals faster than you hit it, and your time is wasted.
How it activates
The activation logic is tied to creeps near the building:
- On by default. With no attacking-team creeps nearby, protection is active.
- Turned off by creeps. A Tier 2 tower has its own 900 radius: your creeps step in, its protection drops. Buildings inside the base, though, listen to the Ancient, and its radius is 4000 — so the whole base loses protection at once, to a single wave.
- 15.5 seconds after. Once the last creep dies the building stays vulnerable for 15 more seconds, plus half a second while the aura itself fades.
- Turns back on. Then protection returns, and regen plus damage reduction restart.
- Dominated creeps do not count. Creeps taken over with Helm of the Overlord and the like no longer disable protection — that loophole was closed in patch 7.36.
That's why a smart push always moves with a creep wave — more in the guide on split-push. The window for pressure is easier to catch at night, when the enemy's vision is shorter: how the day-and-night cycle works we cover separately.
What protection gives
Under backdoor protection a building is nearly invincible solo:
- Regen 180 HP/s. The moment damage lands on the building, it heals 18 health every 0.1 seconds.
- −50% damage. Exactly half of the incoming damage is cut before it ever reaches the health bar.
- −75% from illusions. Illusions hit a protected building for only 25% — you can't raze it with a swarm.
- The threshold is 270 damage per second. That is what you have to put out before any reductions to outpace the regen. Solo, that number almost never adds up.
- Your own deny still lands. The regen only feeds on enemy damage. When you finish off your own tower, protection does not undo it — denying works even under it.
Because of that −75% to illusions, pure backdoor with illusion heroes is ineffective. To actually break protected buildings you need either a creep wave or a hero with big direct damage to structures.
Which buildings have it
Protection isn't everywhere, and that decides what you can backdoor:
- Except T1 and the fountain. Tier 1 towers and the fountain have no protection — you can break them without creeps.
- T2 — individually. Each Tier 2 tower is protected on its own and is not tied to the base at all: knock one out and the rest stay protected.
- Base — shared protection. Tier 3 and Tier 4 towers, the barracks and the Ancient share one protection that originates from the Ancient, and they lose it at the same moment he does.
- Tower order. The next tower in a lane is invulnerable while the previous one stands, and barracks open up after the T3 falls. That is a separate mechanic: backdoor protection is not what makes them invulnerable, and stripping it does not change the order.
So an early T1 backdoor is a valid tactic, but you can't "sneak" a base by bypassing the lanes: everything in the base is under the Ancient's shared protection. A clean tower take, though, evens out the gold and often becomes the backbone of a comeback from a losing position.
How to push correctly
These rules turn a push from wasted time into actual structures, and the objectives you take into one of the most reliable ways to climb MMR:
- Push with a wave. Bring creeps under the tower — without them protection won't drop.
- Don't backdoor the base with illusions. The −75% damage makes it pointless.
- Finish within 15 seconds. After the creeps die you have a short window — don't waste it.
- T1 is the exception. You can and should break them early; there's no protection there.
