On the Internet, it’s not only “always DNS” – it’s also about securing DNS. DNS faces a wide range of attack vectors, each requiring different defensive strategies. Here comes an overview of DNS security, which gives you all the keywords at a glance.
I was presenting at the annual “Wireshark Developer and User Conference“, the SharkFest’25 EU, talking about “Securing DNS – Attacks and Defences“. It covered all the buzzwords related to DNS security, such as malware using DNS, DNS spoofing, DNS exfiltration & tunnelling, while defending them with the keywords as DNSSEC, DoH/DoT, feeds & blocklists, and so on.
Quite many techniques. ;) Luckily, the whole session was recorded. So if you’re interested, have a look!
While I was working on my presentation about “Secure DNS” for this year’s SharkFest, the Wireshark Developer and User Conference, I recognised that I’m still missing some DNS-related packet captures in the Ultimate PCAP, that is DNS over TLS and DNS over HTTPS. And while working on it with the DNSDiag toolkit (thanks, Babak!), I came across DNS over QUIC and DNS over HTTP/3. 😂 Here we go:
I was faced with an interesting customer requirement: An existing guest Wi-Fi should be prefaced with a welcome page for accepting the terms and conditions. Since there was already a Palo Alto Networks firewall in place, could we perhaps use its captive portal directly for this purpose? It’s not about authenticating the users, but only for a single webpage with a simple check button that should appear once a month per device.
TL;DR: While we were able to redirect every device to a welcome page, we were not able to extend the lifetime of those sessions to longer than 24 hours. This might fit for short-term guest Wi-Fis, but is not appropriate for long-term connections aka BYOD. However, this is how we have done it:
Continue reading Misusing Palo’s Captive Portal as a Guest Wi-Fi Welcome Page
Email is still the most common communication protocol on the Internet. And since I was missing some variants of the related protocols, IMAP, POP3, and SMTP in the Ultimate PCAP, I did some captures. ✅ Here are a few details.
Again two more commonly used network protocols for the Ultimate PCAP: the Remote Authentication Dial-In User Service (RADIUS) and the Terminal Access Controller Access-Control System Plus (TACACS+) protocols. Captured with quite some details:
At SharkFest’22 EU, the Annual Wireshark User and Developer Conference, I attended a beginners’ course called “Network Troubleshooting from Scratch”, taught by the great Jasper Bongertz. In the end, we had some high-level discussions concerning various things, one of them was the insight that TCP RSTs are not only sent from a server in case the port is closed, but are also commonly sent (aka spoofed) from firewalls in case a security policy denies the connection. Key question: Can you distinguish between those spoofed vs. real TCP RSTs? Initially, I thought: no, you can’t, cause the firewalls out there do a great job.
It turned out: you can!
This post is about adding an own (trusted) X.509 certificate for the HTTPS GUI of the Cisco Application Policy Infrastructure Controller aka APIC. You can do this via the GUI itself or via the API. Here are both ways:
This is a guest blog post by Erik Hjelmvik, an expert in network forensics and network security monitoring at NETRESEC.
PolarProxy is a transparent TLS proxy that outputs decrypted TLS traffic as PCAP files. PolarProxy doesn’t interfere with the tunnelled data in any way, it simply takes the incoming TLS stream, decrypts it, re-encrypts it and forwards it to the destination. Because of this PolarProxy can be used as a generic TLS decryption proxy for just about any protocol that uses TLS encryption, including HTTPS, HTTP/2, DoH, DoT, FTPS, SMTPS, IMAPS, POP3S and SIP-TLS.
PolarProxy is primarily designed for inspecting otherwise encrypted traffic from malware, such as botnets that use HTTPS for command-and-control of victim PCs. Other popular use cases for PolarProxy is to inspect encrypted traffic from IoT devices and other embedded products or to analyze otherwise encrypted traffic from mobile phones and tablets. The fact that PolarProxy exports the decrypted traffic in a decrypted format without any TLS headers also enables users to inspect the decrypted traffic with products that don’t support TLS decryption, such as intrusion detection and network forensics products like Suricata, Zeek and NetworkMiner.
Quite spontaneous I gave a small talk on the 3rd german DDI (DHCP/DNS/IPAM) user group which took place on June, 17th, 2021. (I was asked to do a talk just two days before the meeting.) It’s based on my blog post about accidental hostname disclosure through the certificate transparency log. To be honest, there’s not much more information in the slides than in my initial blog post. ;D
Continue reading DDIUGv3: Certificate Transparency Disclosure
This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.
The Internet Engineering Task Force (IETF) published the Network Time Security protocol (NTS) as RFC 8915 on October 1, 2020. This new standard offers security mechanisms for the widely used Network Time Protocol v4 (NTPv4), which has been operated mostly unsecured until now. After almost eight years of development, global collaboration, and many interoperability tests of leading NTP software developers, NTS represents a mature security protocol. In this post, I’ll give you a short overview of the development progress of NTS and provide a list of public implementations and NTS secured time servers…
Maybe you’ve heard of Certificate Transparency and its log. Citing Wikipedia: “Certificate Transparency (CT) is an Internet security standard and open source framework for monitoring and auditing digital certificates.” Basically, it gives you information about any public certificate that is issued. Besides its advantages, I thought of one possible problem as it leaks all FQDNs to the public when using TLS certificates, for example from Let’s Encrypt.
A similar problem might arise when using a single X.509 certificate with a couple of DNS names (subject alternative name SAN) from which one should be kept “private”. It will be publicly known as well.
Hence I made a self-experiment in which I generated two certificates with random names, monitoring the authoritative DNS servers as well as the IPv6 addresses of those names in order to check who is resolving/connecting to otherwise unknown hostnames. Here we go:
Continue reading Certificate Transparency & Alternative Name Disclosure
This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.
In the previous posts, I already introduced the Network Time Security (NTS) protocol and described the most important features. Although the specification process has not been completed, there are already some independent NTS implementations and public time servers (IETF106). NTPsec is one of the important representatives of this series and already offers an advanced NTS solution. In this post, I’ll give you a short guide to setting up an NTS-secured NTP client/server with NTPsec.
This is a guest blogpost by Erik Hjelmvik, an expert in network forensics and network security monitoring at NETRESEC.
Wireshark is the default goto tool for analyzing captured network traffic for most network engineers. But there are a few other free and open source alternatives that are sometimes overlooked, one of which is NetworkMiner (disclaimer: I’m the creator of NetworkMiner).
This is a guest blogpost by Martin Langer, Ph.D. student for “Secured Time Synchronization Using Packet-Based Time Protocols” at Ostfalia University of Applied Sciences, Germany.
The Network Time Security protocol (NTS) is close to completion as an Internet standard and will replace the existing security mechanisms in NTP. The introductory article on NTS describes the basic communication process as well as the most important features. Despite high-security efforts, NTS also has its limitations. In this blogpost, I list the strengths and weaknesses of the new authentication mechanism and describe them briefly.
Continue reading Network Time Security – Strengths & Weaknesses