I've been attacked by a dog once, when I was 9 years old (we had just moved to a new state and neighbourhood).
My sister and I were out walking Harley when we were approached by a stray dog (it was a fairly big dog, probably had some Kelpie in him). The dog was following my sister, Harley and I up the street and it wanted to say hello to us and Harley. It actually seemed really friendly, and wasn't aggresive towards Harley at all. We continued to walk away, but because the stray dog was still following us I went to slowly show it my hand and attempt to pat it. This was a huge mistake, but I don't think anyone could have guessed what was going to happen next. It was like the dog's personality changed in a snap! What happened next was very frightning.
The dog let me pat him, then all of a sudden the dog lept up on me, dug it's claws into my arms and was about to bite me on the face!! I was SO terrified.. I was trying with all my strength to push the dog off me, but he was so heavy and wouldn't get off, and it's claws were digging into my arms so hard. I was crying so much and shouting at the dog, and my sister couldn't do anything to help me, Harley was standing there barking and whimpering really loudly while all of this was going on. I seriously thought I was going to die.
Then, all of a sudden Harley lashed forwards, toward the dog, and bit the dog on his ankle! The dog then jumped off me and ran a few strides away, but then turned around and started chasing my sister and I.. We were really terrified at this point. We both ran as fast as we could towards our house (luckily this happened at the end of our street), but we didn't have time to close our gate. We got inside the house just in time. The dog ran up to our front door and waited out there for 2 hours!! It was like the dog was so intent on killing us.
I didn't know how bad my injuries were, but my sleave was torn in one place. My sister rang my mum straight away, and I looked at my arm and it was all bruised and bloody. It was where the dog's claw had cut my arm. It has been 9 years and I STILL have a scar from it. That's one day I will *never* forget, and I have learnt a serious lesson. NEVER pat a (stray) dog when the owner isn't around, or without the owner's permission! Even if it looks and acts friendly. I don't know what would have happened if Harley wasn't with us... He was my life saver.
Anyway, it turns out that the owner of the dog just let his dog wonder around the neighbourhood, and there had been a few accounts of this dog attacking other dogs quite visioucly (in particular, one little dog in our street). This man (the owner) had been reported to the police many times but there was nothing they could really do about it!
After that I was quite wary of bigger dogs, especially when they would approach me.