Hi,
If you run debian, did you update ProFTP via apt-get or synaptic? The news mention only compromised source packages, and the original security bugfix is at least two weeks older than the server hack. You should check when Debian did the last update to their binary package, there's a good chance that these have never been affected. Of course you should run the bugfixed version 1.3.3c.
http://www.net-security.org/secworld.php?id=10243
If you did compile ProFTP yourself, and downloaded the source between Nov 28th and Dec 2nd, your server is likely compromised.
Additionally, you could monitor network activity. Look for the command 'HELP ACIDBITCHEZ' which is mentioned
here, or try it yourself on a connection to your server.