• PORTKNOCKING - A system for stealthy authentication across closed ports.
  communication in which information arrives encoded in the form of connection attempts to closed ports
  Port knocking is a stealthy network authentication system that uses closed ports to carry out identification of trusted users. The system permits manipulation of firewall rules from a remote host across closed ports through encrypted channels.
  bioinformatics centre firewall genome linux network open ports router sciences security source tcp
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