# 5353/UDP Multicast DNS (mDNS) and DNS-SD {% hint style="success" %} 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)
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{% endhint %} ## **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="/pages/n2ZzKzRMPQXJnSf4gUWt" %} [Spoofing LLMNR, NBT-NS, mDNS/DNS and WPAD and Relay Attacks](/hacktricks/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) {% hint style="success" %} 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)
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