My Mini-schnauzer chewed my brother up last week (the brother who most deserved it too, but that's another story ;) ).
He came in my house and he grabbed her when she started barking at him. He's miffed with me (for the b'zillionth time), I apologized...but bottom line is she did what I wanted her to do with any intruder.
Note to self... don't visit najida's house. And especially DON'T pick up barking dog.