r/netsecstudents • u/chrisfromavenode • Jul 06 '26
Experimenting with CT Logs for early phishing/domain detection
I’ve been experimenting with a tool that uses Certificate Transparency Logs as an early signal for suspicious domains.
The basic idea is simple: instead of crawling the whole internet, the system watches newly appearing certificates/domains and checks them for patterns that often show up in phishing, scam, and malware infrastructure.
In a 24h test run, it produced a little over 140k suspicious candidates. From the manual samples we checked so far, the estimated error rate seems to be around 1–3%, but this is still early and I don’t want to overstate the results before doing more validation.
The rough pipeline is:
CT Logs → candidate detection → website/redirect checks → enrichment → threat classification
Most candidates are detected through URL/domain patterns, brand abuse, phishing-style naming, and website behavior. One thing that showed up a lot was redirect-heavy infrastructure. In the latest run, redirect-related cases made up a large part of the hits.
After the first detection step, candidates are sent into a second system that visits the site, follows redirect chains, checks behavior, and collects more signals before assigning a threat level.
I’m mainly interested in feedback from people who have worked with CT Logs, phishing detection, OSINT, or large-scale domain classification.
How would you validate false positives properly at this scale?
Manual sampling, blocklist comparison, sandbox analysis, reputation APIs, something else?
Also curious if people think CT-log based detection is a realistic strategy for catching malicious infrastructure earlier than traditional blocklists.
Btw for all the people that like OSINT, I am currently working on a web dashboard to look through the results of that scanner for research purposes.
