Verified answer

The lab was not bred to be a Guard dog, the chances are, they will bark at the intruder, but as far as attacking, No. Breeds like the German Shepherd, Rottweiler, and Doberman are the ones to look for if you are looking for a capable guardian. Labrador Retrievers are just Watchdogs. Only Bark, No Bite.

Bernese Mountain Dogs are protective of the family, and might pursue to attack, but as far as making contact, I really don't think so. They are a VERY good working breed, much like the German Shepherd and Rottweiler, but I wouldn't consider them to be a great guard dog. They are protective of their family and kids though.

The Lab was not bred to be a guard dog or for protection, so it would be unlikely to really protect you. I don't know about the BM dogs.