hacktricks/network-services-pentesting/5353-udp-multicast-dns-mdns.md

# 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 **_\<Service>.\_tcp or \_\<Service>.\_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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