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Naveen Sunil
Naveen Sunil
Information Technology
10 Jan 2019

Firewall Bypass in Nmap

Few days back on one of the post of Network mapping | CrazyEngineers introduced Nmap tool. 

Well now let's talk on how nmap scanning can be done by evading a firewall. The result will hugely be different. Nmap has got various flags for this purpose. Here I/m listing my frequently used ones.

  1. Using a FIN scan. Firewalls don't log a TCP acknowledgement and hence using the flag -sF sends a FIN request.
  2. Using an Idle scan method with the flag -sI makes the scan very stealthy. One can exploit a trusted IP source. Read more about this at TCP Idle Scan (-sI) | Nmap Network Scanning
  3. Fragmenting packets with flag -f
  4. Spoof source IP address with -S 
  5. Spoof a source port with -g

Well what are your frequently used flags? Or interested in knowing about firewall bypass list in Nmap? Read more at Firewall/IDS Evasion and Spoofing | Nmap Network Scanning