Openwall - scanlogd

scanlogd is a TCP port scan detection tool, originally designed to illustrate various attacks an IDS developer has to deal with, for a Phrack Magazine article. Thus, unlike some of the other port scan detection tools out there, scanlogd is designed to be totally safe to use.

scanlogd supports several packet capture interfaces: the raw socket interface on Linux (which does not require any libraries), libnids, and libpcap.