Astaro Portscan Detection is a netfilter target which will attempt to detect TCP and UDP port scans and log them to syslog. This target is based upon Solar Designer's scanlogd. It suppports mutliple levels of logging, custom prefixes for entries, weighted total port scan detection, and port scan temporal spread detection.
Amber sits in the tcpserver chain for qmail and implements an "amber list" for incoming mail. This neither accepts nor rejects connections, but implements a number of timing-related tricks to fake out spam and virus software that doesn't implement SMTP correctly. For example, it can defer requests from new IP addresses for a few minutes before it starts passing connections on to smtpd, pause and check for programs that send data before the HELO, and otherwise make things rough for bandit bulk mailers.