A simple network monitoring tool that detects and logs (D)DoS attacks with tcpdump. You can read more about this tool here
You can start dosmon with dosmon.pl start & stop it by running dosmon.pl stop.
Configuration files are read from /etc/dosmon/*.conf
On debian you should install perl ofcourse and one necessary module:
apt-get install perl cpan && cpan install Net::Server::Daemonize