UDP Scan

A user diagram protocol (UDP) scan checks for any UDP ports that are deployed on a target. Conversely, the regular scan only scans the TCP ports. UDP scans are normally slower and more difficult than TCP scans.

Syntax

nmap -sU <target>

The -sU option is used to perform a UDP scan on a <target>. It can be combined with any TCP scan type. For example, a stealth (SYN) scan (-sS) checks for UDP and TCP ports in the same run.

Example

The following example runs a UDP scan on the site scanme.nmap.org:

nmap -sU scanme.nmap.org

Note: This is a site explicitly set up for testing Nmap. Scans should only be performed on domains with explicit permissions given to the user.

This results in the following output:

Starting Nmap 7.93 ( https://nmap.org ) at 2022-12-15 09:20 CET
Stats: 0:07:20 elapsed; 0 hosts completed (1 up), 1 undergoing UDP Scan
UDP Scan Timing: About 45.33% done; ETC: 09:36 (0:08:49 remaining)
Nmap scan report for scanme.nmap.org (45.33.32.156)
Host is up (0.21s latency).
Other addresses for scanme.nmap.org (not scanned): 2600:3c01::f03c:91ff:fe18:bb2f
Not shown: 991 closed udp ports (port-unreach)
PORT STATE SERVICE
68/udp open|filtered dhcpc
123/udp open ntp
407/udp open|filtered timbuktu
17487/udp open|filtered unknown
20164/udp open|filtered unknown
49180/udp open|filtered unknown
49186/udp open|filtered unknown
49198/udp open|filtered unknown
50497/udp open|filtered unknown
Nmap done: 1 IP address (1 host up) scanned in 1073.60 seconds

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