Firewalk (computing)

Firewalking is a technique developed by Mike Schiffman and David Goldsmith that utilizes traceroute techniques and TTL values to analyze IP packet responses in order to map networks and determine gateway ACL filters. It is an active reconnaissance network security analysis technique that attempts to determine which layer 4 protocols a specific firewall will allow.

Firewalk is a software tool that performs Firewalking.

To protect a firewall or gateway against firewalking one can block outgoing TTL messages to avoid exposing information about your network. Additionally, using Network address translation is useful to hide internal network addresses.

See also

• Access Control List
• Firewall (computing)
• Traceroute

External links

• Firewalk tool, an Open Source tool that determines gateway ACL filters and maps networks by analyzing IP packets responses.
• WooterWoot, an Open Source set of tools that builds Check Point, Cisco ASA, or Netscreen policies from logfiles.
• Use Firewalk in Linux/UNIX to verify ACLs and check firewall rule sets, article on using Firewalk, by Lori Hyde CCNA.
• firewalk(8) - Linux man page
• GIAC / SANS Institute Description of Firewalking