What are these messages about: “Limiting icmp/open port/closed port response” in my log files?
This is the kernel telling you that some activity is provoking it to send more ICMP or TCP reset (RST) responses than it thinks it should. ICMP responses are often generated as a result of attempted connections to unused UDP ports. TCP resets are generated as a result of attempted connections to unopened TCP ports. Among others, these are the kinds of activities which may cause these messages: • Brute-force denial of service (DoS) attacks (as opposed to single-packet attacks which exploit a specific vulnerability). • Port scans which attempt to connect to a large number of ports (as opposed to only trying a few well-known ports). The first number in the message tells you how many packets the kernel would have sent if the limit was not in place, and the second number tells you the limit. You can control the limit using the net.inet.icmp.
