Security for virtual domains
Our server has a couple of virtual domains. Each domain has different software packages running and so we've been hacked a couple of times. The hacker finds one hole or the other to enter the server. Often we dont know how he broke in. The whole server goes down for a week or two and our administrator (who has done and is doing a wonderful job) spends that time to rebuild the server from scratch. We have backups but its excruciating to rebuild the server and all the domains go down as well. We're thinking of installing Snort. Maybe it will stop the attacks.
Is there any way to keep virtual domains separate from each other so if a hacker came in through a security hole in one domain, he couldnt effect the other domains or the server as a whole? Surely I'm thinking there must be a way to isolate and provide security for each domain.