Cybersecurity Researchers Reveal Quirky User Agent Strings in Honeypot Logs
A closer look at honeypot logs has revealed a treasure trove of curiosity-inducing user agent strings (UAS), showcasing the creative and often humorous ways attackers attempt to blend in with legitimate traffic. The findings, uncovered by cybersecurity researcher Didier Stevens, expose the tactics used by malicious actors to evade detection while scanning networks.
The logs, which are essentially decoy systems designed to mimic real-world targets, have revealed a range of unusual UAS that stand out from the norm. For instance, some scans include phrases such as “authorized” or “scan,” while others incorporate wordplay and even attempt to discredit their own actions. This trend suggests that attackers are becoming increasingly aware of the importance of user agent manipulation in evading detection.
One notable observation is the prevalence of masscan variants, including a rather tongue-in-cheek “KGB variant.” Masscan is a popular open-source scanning tool used by both legitimate and malicious actors to identify vulnerabilities on networks. The inclusion of such variants raises questions about the intentions behind these scans, particularly when they are accompanied by URLs or email addresses for further communication.
The use of complete lists of UAS in requests is another tactic observed in the logs. This approach allows scanners to dynamically select a new user agent string for each request, often without proper sanitization. As a result, separator lines intended to group UAS together are being used as legitimate strings, highlighting the lack of quality control in these lists.
Furthermore, some attackers have been caught exploiting vulnerabilities in how UAS are parsed, with instances of Shellshock still appearing in logs despite its age. This demonstrates that even after years of advisories and patches, some attackers continue to rely on outdated exploits.
The most intriguing discovery, however, is the presence of requests specifically targeting servers streaming GPS correction data via the NTRIP protocol. The inclusion of a NTRIP header in these requests suggests that attackers are actively scanning for this particular type of server, potentially indicating an interest in compromising navigation systems or disrupting critical infrastructure.
As cybersecurity professionals and enthusiasts, it’s essential to stay vigilant and informed about emerging trends in attacker tactics. While the quirks revealed in these honeypot logs may seem amusing at first glance, they underscore the importance of staying up-to-date with the latest threats and vulnerabilities. By understanding how attackers manipulate user agent strings, we can better design our detection mechanisms and improve our overall security posture.
In light of this research, it’s crucial for organizations to regularly review their network traffic and update their scanning tools to account for emerging tactics like these. Moreover, by monitoring honeypot logs and staying informed about new developments in the cybersecurity landscape, we can collectively work towards creating a safer online environment.
Source: SANS ISC — 2026-10-04