Tag Archives: IoT

Why should I run own NTP Servers?

… since we all can use pool.ntp.org ? Easy answer: Many modern (security) techniques rely on accurate time. Certificate validation, two-factor authentication, backup auto-deletion, logs generation, and many more. Meanwhile we use an unauthenticated protocol (via stateless UDP) from unauthenticated sources (NTP pool) to rely on! Really?

TL;DR: If you want to operate a secure environment you should use your own on-site stratum 1 NTP servers along with authentication. This is the only way to eliminate time spoofing attacks from the outside. Don’t reduce your overall security to a stateless and unauthenticated (read: easy-to-spoof) network protocol!

If you are using couple of different NTP sources it might be not that easy for an attacker to spoof your time – though not unfeasible at all. And think about small routers with VPN endpoints and DNSSEC resolving enabled, or IoT devices such as cameras or door openers – they don’t even have a real-time clock with battery inside. They fully rely on NTP.

This is what this blogpost series is all about. Let’s dig into it. ;)

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Yamaha R-N500 Network Receiver Packet Capture

Last but not least I was interested which “home-calling” connections my Yamaha R-N500 Network Receiver initiates. In my previous post I already analyzed the open ports within the network, while I showed a complete Apple AirPlay capture here. This time I was only interested in outgoing TCP/UDP connections to the Internet as well as how the Yamaha App “NP Controller” communicates with the receiver.

It turned out that it was not easy for me to fully analyze such a packet trace even though only a couple of connections were made. It consists of many protocols that I am not familiar with such as UPnP, MDNS, SSDP, and RTP. Anyway, ere we go:

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Yamaha R-N500 Network Receiver Port Scan

During my analysis of Apple AirPlay connections to my Yamaha Network Receiver I was also interested in which TCP/UDP ports are opened on this audio device at all. Hence I did a basic port scan with Nmap for both transport layer protocols. (In an upcoming blogpost I am analyzing a packet capture from the Yamaha receiver which will show more details about the used ports and outgoing connections.) At first here are the Nmap results:

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Apple AirPlay Capture

I was interested in how Apple AirPlay works in my network. I am using an iPad to stream music to a Yamaha R-N500 network receiver. There is a great Unofficial AirPlay Protocol Specification which already shows many details about the used protocols. But since I am a networking guy I captured the whole process in order to analyze it with Wireshark.

Following is a downloadable pcap if you want to have a look at it by yourself as well as some Wireshark and NetworkMiner screenshots for a first glance.

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