udp port scanning

Charlie Yianni

min read

What is UDP Port Scanning?

UDP port scanning is a type of network scanning that identifies open or closed User Datagram Protocol (UDP) ports on a system. These scans help security teams understand which services are exposed and whether any vulnerabilities could be exploited by attackers.

Why UDP Port Scanning Matters

While TCP is more commonly used, many critical services rely on UDP (e.g., DNS, DHCP, and SNMP). Because UDP is connectionless and harder to monitor, attackers often target it to exploit misconfigurations or overlooked services. Scanning UDP ports is essential for:

Identifying exposed or unnecessary services
Detecting potential misconfigurations
Understanding the full attack surface beyond TCP

How UDP Port Scanning Works

UDP scanning sends packets to specific ports and analyzes the responses (or lack of them) to determine if a port is open, closed, or filtered. Unlike TCP scans, the absence of a response can indicate an open port, which makes UDP scanning slower and more complex to interpret.

Intruder’s Approach to UDP Port Scanning

Intruder performs comprehensive port scanning as part of every full network scan:

Checks all 65,535 TCP ports and 100 of the most common UDP ports
Provides a clear view of which services are exposed and their associated risks
Sends email, Teams, and Slack notifications when new ports open

Common UDP ports Intruder checks include DNS (53), NTP (123), SNMP (161), and more (you can find the full list here).

Why This Matters for Security

Unmonitored UDP services can become an easy entry point for attackers. By regularly scanning UDP ports alongside TCP, organizations gain a complete picture of their network security posture.

Ready to secure your UDP services? Start your free trial to scan and protect your network today.