Attack Dogs will sniff you out way before the Royal Army does and can jeopardize your position almost instantly. The best way to get rid of one (or more) while keeping the element of surprise is to lure it out of the view of enemy troops with bait, then shooting it with a silenced weapon. Royal Guard Kennels is the only outpost where these dogs are found.
They are also found on certain side quests and main missions. Such as assassination quests, and bomb defusing ones. On main missions, they can be found on the level where you must sneak into the City of Pain, and also during the Brick Factory and Durgesh prison missions.
Attack dogs are aggressive but run relatively slowly. Unlike their Guard Dog predecessors in Far Cry 3 that would attack creatures and predators larger than themselves, these dogs don't. Instead they will run from any wild predator. Wild herbivores will run from them but they won't give chase. If an enemy is killed and an attack dog is near by, it will bark alerting its comrades of the commotion, thereby putting them on high alert.
The breed of these dogs are not specified, but they most resemble a rottweiler with cropped ears, not commonly done on the breed but possible.