I've added a file in the templates-custom/.../masq directory for ipchains rules to block various things. Like www access from the entire 24.x.x.x range to reduce worm traffic, smtp and pop3 access from the .cn domains because of their mail relay attempts, and all access by RoadRunners scanners just because I don't care for their policies.
It would be nice to have a server manager panel to do this. Something with a place to put the source ip you want to block/allow/forward, compatible with CIDR notation and check boxes for the most common services with a place to add a list of custom ports. Similar settings for the destination too. And one thing that seems to get left out of most utilities, a text field to note why the rule was put in place.