The GreyNoise Labs team is proud to have hosted the GreyNoise NoiseFest 2023 CTF - who knows if we will do it again, but we had fun, so here’s a walkthrough on how and why we did it.

But first: your winners!! 

  • 1st: t3mp3st w/ 4060 points in 5 days, 2 hours, 24 minutes and 19 seconds
  • 2nd: An00bRektn w/ 3060 points in 1 day, 2 hours, 9 minutes and 57 seconds
  • 3rd: jk42 w/ 3060 points in 19 hours, 35 minutes and 27 seconds
  • 4th: mtaggart w/ 3060 points in 1 day, 0 hours, 24 minutes and 18 seconds
  • Honorable Mention: MyDFIR for the early lead 

We’re incredibly proud of everybody who even attempted to play - all 280 participants! Our community team has contacted the winners, and they will be receiving some sweet swag as a prize, plus 1st, 2nd, and 3rd places are getting a beautiful trophy.

Crafting the CTF was one of the best parts of hosting the competition. Competitors in the CTF may have noticed that there was no usage of GreyNoise - and that was by design. When we thought about all the cool things we do daily on the Labs team, we narrowed it down to around 25 tags with CVEs that have led us down rabbit holes or taught us something interesting about how the internet works.

We used these selected examples and packaged them in industry standard PCAP format and set our community loose on the CTF challenges. This allowed us to observe the methods, tools, and pain points in dealing with network traffic that may defy typical expectations. We know that this format of network capture is the highest level of proof that something occurred - the direct record of bytes on the wire. A detection engineer is not only familiar with PCAP but may even live in it daily, noticing how bytes live and breathe just as the GreyNoise Labs team does.

Our new sensor fleet also captures full PCAP, and we wanted to hype that fact! Any difficulties encountered with a single-packet CTF challenge will be grossly exacerbated when working with millions of real-world packets. We’re greatly looking forward to analyzing the pain points from this CTF and providing the tooling that our Detection Labs team and the community need to make network analysis a pleasure to work with. Your feedback has been heard!

(The final scoreboard)

So we learned some things about hosting a CTF - mainly that creating “medium level” challenges in a PCAP-based CTF is hard. We also learned that we like trivia - the challenge “fullsignature” is an excellent example of this, where the answer was the name of the patent holder and original author for the MSMQ protocol. Most importantly, we learned that our community is SUPER SMART in PCAP. Some of the players have done writeups already (this one by An00bRektn, or this one by t3mp3st), and if you’d like to walk through the challenges yourself, we’ve uploaded the challenges and associated PCAP to GitHub at 

Altogether, we learned a lot from this experience and had a great time crafting and solving each other’s challenges here on the GreyNoise Labs team. We look forward to hosting again! 

This article is a summary of the full, in-depth version on the GreyNoise Labs blog.
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