Danger Zone

The Danger Zone (also called the aggro bubble or aggro circle) is the white transparent circle surrounding your character on the compass. Any hostile mob that enters the Danger Zone immediately aggros and begins its attack routine.

Notes:

 * Mobs consisted of level 0, level 1, or sometimes level 2 will not engage in attacking the player in most cases (when approached). One exception is Skale Broodcallers in pre-searing Ascalon, who engage anytime a player enters their danger zone.
 * If a higher level foe does engage you, the nearby lower level (levels 0, 1 and 2) mobs will also engage in attacks. This can be observed in Lakeside County, in pre-searing Ascalon, as whenever a Skale Broodcaller approaches and attacks the player, the level 0 River Skale Tads and level 1 River Skales will also begin to attack.
 * Some mobs move to attack even when outside your Danger Zone. For example the Kournan Spotters as part of groups of Kournans will notice you at approximately twice the aggro radius and the group will move to attack.

Links

 * Range for detailed informations.