Understanding Guide to Nmap Firewall Scan (Part 1)

Hello friends, several times you might have used NMAP to performing Network scanning for enumerating active Port services of target machine but in some scenario it is not possible to perform scanning  with help of basic scan method especially in case of firewall filter.

Today we are going to demonstate “Nmap firewall scan” by making use of Iptable rules and try to bypass firewall filter to perfrom NMAP Advance scanning. 

Let’s Begin!!

Attacker’s IP: [kali linux]

Target’s IP: [ubuntu]


Open the terminal in your kali linux and execute following command to perform TCP[sT] scan for open port enumeration.

nmap -sT -p22

From given below image you can observe we had scanned port 22 as result it has shown Port 22 is Open for SSH service.

When you will use wireshark in order to capture the packet send in the case of TCP while network is being scanning , here you need to notice few things such as “flag,Total length and time to live[TTL]” [in layer3].

Following table contains detail of Flag, Data length and TTL in diffrent scanning method:


Scan Name Flag Data Length TTL
-sT (TCP) SYN →

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Understanding Guide to Nmap Firewall Scan (Part 1) Understanding Guide to Nmap Firewall Scan (Part 1) Reviewed by Unknown on 7:45 AM Rating: 5