Basic Packet Filtering

• Naming services--
  • DNS (53/udp) to all machines which are not DNS servers, DNS zone transfers (53/tcp) except from external secondaries
• Mail
  • SMTP (25/tcp) to all machines, which are not external mail relays
  • POP (109/tcp and 110/tcp)
  • IMAP (143/tcp)
• Web (except to external Web servers)
  • HTTP (80/tcp)
  • SSL (443/tcp)
  • may also want to block common high-order HTTP port choices (8000/tcp, 8080/tcp, 8888/tcp, etc.)

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 Last change: Monday, June 21, 2004 3:47 pm
 Unless otherwise expressly stated, all original material on this page created by Diomidis Spinellis is licensed under a Creative Commons Attribution-Share Alike 3.0 Greece License.