Which tools to monitor traffic and alert ?

[Joel Carnat]

Hi,

I run several standard services (Web, Mail, DNS, …) and have configured Munin 
to graph traffic and see what happened.

I was wondering what was the usual OpenBSD way for proactive/real-time traffic 
monitoring and alerting.
That is, which software to use that would, for example, read HTTPD logs and 
alert if req/sec from same IP is over 50 ?

Looking at the ports, I saw « snort » but I was wondering if there were lighter 
tools for such tasks.

Thanks,
    Jo