We may be able to help. The MW3 Server Admin (MW3SA) allows you to kick/ban players who break your rules.
MW3SA now tracks user IDs instead of IP addresses. Instead of having to re-ban every time someone gets a new IP address, MW3SA can take care of this.
Our new Python based script support allows you to take the tool to the next level. We expect to see advanced features such as ban lists in the future. Any programmer can simply download the script version of the tool and extend it via a few very simple integration points.
We'll keep improving MW3SA. With the built-in update check you will be informed when an update is available. Experiencing application crashes? Tell us and we'll start working on it!
As an improvement over our old system, we now ship several versions of the application. This includes a normal and a script version, plus lightweight packages of these. The lightweight packages don't include the requirements and are therefore more suitable for updates.
Some people may have issues installing the tool. Make sure that you have installed all requirements and use at least Windows 7. Previous versions of Windows may work but are not supported.
The tool will not work if you are behind a proxy. Luckily, the game itself won't work behind a proxy either, so that's not really a problem. VPNs are fine.
If the tips above did not help and you are still experiencing difficulties with the tool, please shoot us an email. Include a full description of the problem and maybe some steps to reproduce. Very short or incomplete bug reports (such as "PATHETIC, it doesn't work.") will be ignored.
I'm not only a programmer, I also like helping people with issues they're having (which may explain why I wrote MW2SA and MW3SA). I've written a guide that should help you solve some network issues which may help you get MW3SA working better. For example, with a strict NAT you aren't going to be able to host which will definitely be a problem.