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.
These details are provided for information only. No information here is legal advice and should not be used as such.