Laws of the State of New Hampshire

The bad_tcp_packets chain The bad_tcp_packets chain is devoted to contain rules that inspect incoming packets for malformed headers or other problems. As it is, we have only chosen to include a packet filter which blocks all incoming TCP packets that are considered as NEW but do not have the SYN bit set, as well as a rule that blocks SYN/ACK packets that are considered NEW. This chain could be used to check for all possible inconsistencies, such as above or XMAS port-scans etc. We could also add rules that looks for state INVALID. If you want to fully understand the NEW not SYN, you need to look at the State NEW packets but no SYN bit set section in the Common problems and questions appendix regarding state NEW and non-SYN packets getting through other rules. These packets could be allowed under certain circumstances but in 99% of the cases we wouldn't want these packets to get through. Hence, we log them to our logs and then we DROP them. The reason that we REJECT SYN/ACK packets that are considered NEW is also very simple ...»