Port 5353Multicast DNS
Multicast DNS (mDNS) is a zero-configuration networking protocol that facilitates hostname resolution without a central DNS server, primarily within small local networks. It allows devices to discover each other and communicate seamlessly, especially helpful in consumer and IoT environments where manual network configuration is impractical..
- transport
- udp
- in transit
- cleartext
- assignment
- official
- risk
- 2/10
- lookups
- 13,394
single transport
payload readable on path
registered with iana
safe
rank 274 of 993 · top 28%
Technical Details
what runs on :5353Multicast DNS (mDNS) is a protocol designed for resolving hostnames to IP addresses within small networks that lack a dedicated DNS server. This is accomplished by leveraging multicast UDP packets sent to all devices on the local subnet using the reserved address 224.0.0.251 on UDP port 5353. When a device queries for a hostname, it multicasts the request, and the target system responds directly if it owns the address.
mDNS is a core component of Zero-Configuration Networking (ZeroConf), popularly implemented in Apple's Bonjour service. It cooperates with DNS Service Discovery (DNS-SD) to offer a combined solution for locating network services like printers, file sharing, or media streaming devices without manual configurations or infrastructure.
Technically, mDNS reuses much of the classic DNS packet structure and semantics but restricts query scope by sending messages to a multicast address. Consequently, it reduces the need for centralized management in small or dynamic environments. However, as it relies heavily on multicast, its operation is bounded to the local subnet and not suitable for wide-area resolution.
Security Information
exposure of :5353risk score
2/ 10safe
routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.
network services averages 3.9 across 604 ports — this one sits 1.9 below.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
udp
udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite
security overview
Common vulnerabilities:
- Susceptibility to spoofing attacks where malicious devices respond with forged answers, potentially redirecting traffic.
- Potential information leakage, as hostname and service details are broadcasted to all devices on the subnet.
- Possible amplification vector for DDoS attacks through spoofed multicast queries that elicit numerous responses.
Common mitigations:
- Segmenting networks with VLANs or firewall rules to limit the multicast domain.
- Adding filtering rules on switches or routers to restrict or control mDNS traffic.
- Disabling mDNS on sensitive or unmanaged devices to minimize exposure.
- Implementing monitoring solutions to detect abnormal multicast traffic patterns indicating misuse.
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risk mix of the 8 listed
- caution100%
0 of 8 encrypted