Another follow-up after coming back to the forum.
With
rsyslog, you can easily do this. The primary trick is that you include a text with each of the iptables log entries. Then, you can use so-called "contains" searches, which check for the text in question inside the log entries. This can be done as part of regular rule processing.
Note that rsyslog is the standard syslogd on Fedora 8+ and will be the standard on the next release of Debian. So you may already using it and just need to deploy the necessary rules. As this topic seems to be of interest to many people (judging from the access count), I'll probably write a HOWTO. If so, I'll post the link here (so it probably is a good idea to subscribe to the thread if you are intersted in the HOWTO

).