Weird Referrers! Just started last week. Any ideas?

Last week, I've started to receive a large amount of traffic to pages that don't exist resulting in them seeing a 404 page. Then most just bounce.

My referring urls look like this :

mysite .com/BbUECqfF/index.html


and so on. All are from unique IP's and from all over the world.

Any ideas as to what this is all about?

Ive noticed a few of these but thought it was a Google thing.