Any dog (breed) can attack, it's up to the owner to make sure the dog has no ability to attack. You really have to be able to read your dog's body language in different situations to be able to predict how it will act or react. Most of the Dobies I've met were nice dogs, pretty calm at first meeting a stranger, but warmed up quickly when they sensed from their owners that I was a nice stranger.

FlatCoats mentioned the www.akc.org for breed info. You can also find Dobie breed clubs that can give you referrals to good breeders and you can find Dobie rescues all on the AKC's website. I mentioned this to someone on here before. Stay away from classified adds in the paper and magazines, people on the side of the road, parking lots or flea markets. They are all backyard breeders out to make money and they pretty much damage the breed. Do lots of homework and shop around. Don't pass up the rescue option. Most rescued Dobies are purebred and have already gone through the puppy stages. What you see is what you get with an adult dog.

You can use this to help you weed out the good and bad breeders:

http://www.geocities.com/Petsburgh/Fair/1901/chart.html