I have a bunch of sites inundated by bots. I'll have a site in the US that all of a sudden uses all my server memory at a time where 99% of the country is asleep. I've used some of the security plug-ins, but have not found them to be very helpful in terms of blocking all these malicious bots. Has anybody else found something that will actually block all these attacks??

Does anyone know if is WP AdCenter Pro still maintained? There hasn't been any updates in a long time and when you go to contact them, their forms do not go through. It does look like they're still selling the plug-in, but as it hasn't been updated for the last few versions of WordPress, it seems like it is out of business.