Sponsored by: Safe Instrument (https://safeinst.com/)
Netfilter module for service protection based on knocking technique. The hidden services would be available to the client if the client knocked a sequence of specific ports (also custom TCP header like SYN+PUSH+ACK+RST flag) in accordance with the agreement made with the server. The knocking technique can be used for Defense In Depths and protect services like SSH, RDP, or VPN.