Have you checked your systems lately for the Logjam attack vulnerability? If not, I want to provide some expertise from my years in cybersecurity on exactly how to test and remediate this important TLS weakness.
In this post, I‘ll overview how to check both your browsers and servers for Logjam vulnerability, explain configuration changes to block it, and dig deeper into why this dusty 2015 bug still matters in 2023. My aim is to equip you with the insights needed to hunt down Logjam and take a layered approach to shoring up transport encryption.
Why You Still Need to Plug "Logjam" in 2023
First disclosed May 2015 by a team of leading cryptographers, the Logjam attack leverages flaws in TLS encryption to downgrade connections and access web traffic. Years later, Logjam remains relevant due to continued flaws in testing and hardening processes:
- 8.4% of the Alexa Top Million domains showed Logjam vulnerabilities in 2022 testing [Source]
- Recent scans found ~2% of popular sites still exhibit Logjam weaknesses [Source]
While a 2% frequency seems low, exposure on highly-trafficked sites poses privacy and financial risks to millions of users. And automated attacks mean vulnerabilities get probed constantly.
The chart below summarizes recent prevalence data that informed cyber threat intelligence services have gathered regarding continued Logjam vulnerabilities across popular web domains:
| Year | % Sites Still Vulnerable | Source |
|---|---|---|
| 2022 | 1.8% | Venafi Labs |
| 2022 | 8.4% | Scott Helme |
So in our modern threat landscape, overlooking "dated" bugs like Logjam is risky. Use the rest of this guide to self-audit both your browsing clients and web servers, then lock down any weaknesses with some simple configuration tweaks I‘ll demonstrate.
Testing Your Browser‘s Susceptibility
The first smart step is checking your client-side exposure…
