STUN Behavior Discovery over TCP

STUN-BEHAVIOR is a protocol used to determine the behavior of Network Address Translation (NAT) devices. It helps in establishing peer-to-peer connections by identifying how a NAT device handles incoming and outgoing traffic. This is crucial for applications like VoIP and online gaming.

What is STUN Behavior Discovery over TCP

STUN-BEHAVIOR, or Session Traversal Utilities for NAT, is a protocol designed to assist devices behind NAT (Network Address Translation) in establishing peer-to-peer connections. NAT devices often create challenges for direct communication between devices because they modify IP addresses and port numbers. STUN-BEHAVIOR helps in identifying the specific behavior of a NAT device, which is essential for applications that require direct peer-to-peer communication, such as VoIP (Voice over Internet Protocol) and online gaming.

The protocol works by sending requests from a client to a STUN server, which then responds with information about the NAT device's behavior. This information can include how the NAT device handles incoming and outgoing traffic, whether it uses endpoint-independent mapping, and how it manages port preservation. By understanding these behaviors, applications can better navigate the complexities of NAT and establish more reliable connections.

STUN-BEHAVIOR is particularly important in scenarios where low latency and high reliability are crucial. For example, in VoIP applications, any delay or disruption in the connection can significantly impact the quality of the call. Similarly, in online gaming, a stable and low-latency connection is essential for a good user experience. By using STUN-BEHAVIOR, developers can optimize their applications to work more effectively in NAT environments, thereby improving overall performance and user satisfaction.

STUN Behavior Discovery over TCP runs on TCP and UDP port 3478 and is official IANA port.

Security risk

If port 3478 is open and the STUN-BEHAVIOR service is running, it could potentially be exploited by attackers to gather information about the network's NAT behavior. This information could be used to bypass security measures or to launch targeted attacks. Therefore, it is important to secure this port and monitor its usage to mitigate potential risks.

In our UFW tutorial you can follow instructions how you can configure UFW to close port 3478. Use StackChanges to monitor if the STUN Behavior Discovery over TCP port is closed and stays closed. StackChanges will send an alert if port 3478 is open again.