# 5353/UDP Multicast DNS (mDNS) and DNS-SD
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## **Basic Information**
**Multicast DNS (mDNS)** enables **DNS-like operations** within local networks without needing a traditional DNS server. It operates on **UDP port 5353** and allows devices to discover each other and their services, commonly seen in various IoT devices. **DNS Service Discovery (DNS-SD)**, often used alongside mDNS, aids in identifying services available on the network through standard DNS queries.
```
PORT STATE SERVICE
5353/udp open zeroconf
```
### **Operation of mDNS**
In environments without a standard DNS server, mDNS allows devices to resolve domain names ending in **.local** by querying the multicast address **224.0.0.251** (IPv4) or **FF02::FB** (IPv6). Important aspects of mDNS include a **Time-to-Live (TTL)** value indicating record validity and a **QU bit** distinguishing between unicast and multicast queries. Security-wise, it's crucial for mDNS implementations to verify that the packet's source address aligns with the local subnet.
### **Functioning of DNS-SD**
DNS-SD facilitates the discovery of network services by querying for pointer records (PTR) that map service types to their instances. Services are identified using a **_\.\_tcp or \_\.\_udp** pattern within the **.local** domain, leading to the discovery of corresponding **SRV** and **TXT records** which provide detailed service information.
### **Network Exploration**
#### **nmap Usage**
A useful command for scanning the local network for mDNS services is:
```bash
nmap -Pn -sUC -p5353 [target IP address]
```
This command helps identify open mDNS ports and the services advertised over them.
#### **Network Enumeration with Pholus**
To actively send mDNS requests and capture traffic, the **Pholus** tool can be utilized as follows:
```bash
sudo python3 pholus3.py [network interface] -rq -stimeout 10
```
## Attacks
### **Exploiting mDNS Probing**
An attack vector involves sending spoofed responses to mDNS probes, suggesting that all potential names are already in use, thus hindering new devices from selecting a unique name. This can be executed using:
```bash
sudo python pholus.py [network interface] -afre -stimeout 1000
```
This technique effectively blocks new devices from registering their services on the network.
**In summary**, understanding the workings of mDNS and DNS-SD is crucial for network management and security. Tools like **nmap** and **Pholus** offer valuable insights into local network services, while awareness of potential vulnerabilities helps in safeguarding against attacks.
### Spoofing/MitM
The most interesting attack you can perform over this service is to perform a **MitM** in the **communication between the client and the real server**. You might be able to obtain sensitive files (MitM the communication with the printer) of even credentials (Windows authentication).\
For more information check:
{% content-ref url="../generic-methodologies-and-resources/pentesting-network/spoofing-llmnr-nbt-ns-mdns-dns-and-wpad-and-relay-attacks.md" %}
[spoofing-llmnr-nbt-ns-mdns-dns-and-wpad-and-relay-attacks.md](../generic-methodologies-and-resources/pentesting-network/spoofing-llmnr-nbt-ns-mdns-dns-and-wpad-and-relay-attacks.md)
{% endcontent-ref %}
## References
* [Practical IoT Hacking: The Definitive Guide to Attacking the Internet of Things](https://books.google.co.uk/books/about/Practical\_IoT\_Hacking.html?id=GbYEEAAAQBAJ\&redir\_esc=y)
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Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\
Learn & practice GCP Hacking: [**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)
Support HackTricks
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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