I have a dv (Dedicated Virtual) server at Mediatemple where I am hosting over 700 Wordpress blogs. Lately I have been facing a problem with comment spam wherein my the server memory utilization shoots up and Apache crashes. I have resorted to using Plesk's firewall module to regularly detect spamming hosts and deny them. But knowing that spammers aren't bound to single IP addresses, I know that this is not going to be a feasible solution in the long run. Also Mediatemple has a cap of 200 IPs on the no. of IPs that can be blocked in this manner. I have already consumed 100+ in a week. And new IPs keep on coming daily. Everyday I have to check the sites comsuming most bandwidth, then check their Apache logs to determine spamming IPs (am relying on project honeypot for this). But I definitely need a better solution than this going ahead.
Can anyone kindly suggest an tool to combat such kind of a problem? Thanks in advance.