scanlogd is a system daemon which attempts to log all portscans of a host to the syslog, in a secure fashion.
You can download it from the following link: https://packetstormsecurity.com/files/download/161754/scanlogd-2.2.8.tar.gz
Source: https://packetstormsecurity.com/files/161754/scanlogd-2.2.8.html