Nmap 6: Network Exploration and Security Auditing Cookbook

Discovering stateful firewalls by using a TCP ACK scan

The TCP ACK scanning technique uses packets with the flag ACK on to try to determine if a port is filtered. This technique comes handy when checking if the firewall protecting a host is stateful or stateless.

This recipe shows how to perform TCP ACK port scanning by using Nmap.

How to do it...

Open your terminal and type the following command:

#nmap -sA <target>

The output follows the standard port format:

# nmap -sA 192.168.1.254


Nmap scan report for 192.168.1.254
Host is up (0.024s latency).
All 1000 scanned ports on 192.168.1.254 are unfiltered
MAC Address: 5C:4C:A9:F2:DC:7C (Huawei Device Co.)

How it works...

The argument -sA tells Nmap to launch a TCP ACK port scan against the target host. ...