PScanDetect version 0.8 is a utility that will detect TCP-based portscans. Tested under FreeBSD 5.1, OpenBSD 3.3, and Slackware Linux 9.0.
You can download it from the following link: https://packetstormsecurity.com/files/download/32399/PScanDetect-0.8.c
Source: https://packetstormsecurity.com/files/32399/PScanDetect-0.8.c.html