I was attacked by a huge owl recently. It drew blood, and really hurt. I can confirm it was entirely silent, in contrast to being attacked by a crow, which makes an almost-avoidable swooshing sound.
I got accidentally attacked by a hawk of some sort. I was walking on a university campus pathway and got thwacked by a hawk jumping off of a pole. Turns out I was merely between it and its prey - it was about to swoop a squirrel. It bounced off me, ignored my existence entirely, and kept chasing the squirrel. Knocked me a bit off balance, but the bird appeared fine and so was I.
Why would an owl attack a huge mammal like a human? Are you a particularly short person? Do owls attack other large mammals like deers, horses, bears etc? That's very scary.
To defend their nest, of course. They don't make prisoners and aim for the face and eyes of anybody trying to steal eggs or owlets.
But most owls nest in big threes high above the soil, so the probability of an attack is really low. Probably there was a fallen owlet hidden close to you.
Sometimes your hair or hat can look like a tasty meal. Sometimes it's territorial, if you're getting too close to a nest or whatever. Usually it's one of those two.
A long time ago, when I had much longer hair and would go running just about every day, there was a block on my route where a bird would swoop down constantly and attack me. I think it thought my hair was a bunch of worms or something. It was a smaller bird, it couldn't really hurt me, but fuck that thing flying around my face was terrifying. I quickly changed routes once I realized it wasn't going to stop.
I got hit by an owl one night while calling coyotes - I was sitting in thick brush, wearing a furry bomber hat and using a mouth call that simulates a distressed rodent. I got lucky and it just grabbed the hat, but it sure surprised the hell out of me and after that I switched to an electronic caller for night hunting. After I bought a night vision rig I was astonished to learn how many owls were swooping on my sets at night.
I think most owls are afraid of humans but birds have intimidation power above their weight and if an owl learns it can push people around it might keep doing so.
Like others have said, they are territorial and they protect their young. You need to be quite careful. The Ural Owl is no joke, it cannot kill you, but it can destroy your sight because it is known to attack the eyes.
I would think it's extremely rare. I recently frightened an enormous great horned owl that had a baby in its nest. Rather than attack, the parent flew to another cliff which set off a bunch of smaller birds cawing and swooping at it. It was a huge commotion and the owl was getting dive bombed relentlessly, but the parent owl held its ground, drawing attention away from its baby. I have a ton of respect for that animal.
Whenever I make any kind of attempt at humor on HN, I get downvoted and told that this isn't the place for jokes but serious discussion. Since the quality of the comments on HN are why I come back every day, I don't disagree.