I was almost hacked into. It only happened after I allowed images in posts. (fopen wrappers=on)
Please set the Knowledge Base to not allow posting. I had someone almost hack in.
He was able to (as a user), but was just a guest, write an article.
Just set the permissions to not allow posting to the Knowledge base, and you will be better off.
The user name was a lot of letters and numbers. ctracker kept them out. I have a record of it in the ctracker database.