Forum Spam attack?
 

Hello, I have recently started my forum and just about an hour ago it appeared to have come under attack. I had a few different IP ranges that were all opening multiple sessions and each one appearing as a separate "guest". I banned these IP ranges, and the flooding seems to be stopping for now.

But now my question is what could this actually have been? And how can I prevent this?

During this "attack" my website was going quite slow, but still functional. I turned off access for a few minutes while I installed a spambot plugin and turned it back on.

I have attached a screenshot of my "who's online" in case someone wanted to see it.
Attached Images

• https://www.vbulletin.com/forum/images/attach/png.gif screensht.png‎ (219.8 KB)