I found as soon as I got to Mournhold the attacks stopped (actually I was only attacked twice altogether). To get to mournhold, first talk to a guard (eg a Hlaalu guard in Balmora, Redoran guard in Ald'ruhn etc) about the attacks, and they'll tell you to go to Ebonheart. Then go to the bridge between the castle and the legion garrison and you'll find a guy wandering around who you can talk to about Mournhold. He'll tell you about the chick just inside the castle who can transport you there. Hope my directions made sense
