Alaskan Malamutes are generally not aggressive dogs, but aggressiveness in dogs does not only depend of the breed of the dog, in most cases depends on the way of bringing.
When we talking about behavior of the people, Malamutes are very calm dogs, especially when children are around. They are very careful with people they do not know, but will never attack first. If you are looking for a dog that will keep your house safe you are not in the right place but with its size and roars, Alaskan Malamute will scare an unknown man who will remain in front of the fence and invite you to introduce into the yard.
Malamutes can be very aggressive towards other animals if do not grow up with them and not be sufficiently socialized.
Conclusion: Alaskan Malamutes are great friends of the people and will never attack first, but they look like the Arctic wolf will distract everyone who have bad intentions.