I've been asked to set up some monitoring for a clients server. They seem to be extremely paranoid about security since they are about to start taking credit card orders. I have never personally used any monitoring software so I thought I'd see what you guys have used?

I have a meeting Thursday about it so I don't have any details yet but I just wanted to look into a few things before hand so I would be somewhat prepared.

Any suggestions? Good experiences or bad?

I'll try to remember to ask our sysadmin tomorrow, but IIRc he uses Nagios.

Awesome, thanks. I will take a look at Nagios.

I think they are primarily concerned with security, if that matters.

Just asked, he does indeed use Nagios for server monitoring, and recommends Nessus for security testing.

Sweet, thanks for asking! I will look into both of those.