Masking Email Addresses in RADIUS Logs for Security and Compliance
The log file is open on your screen. Every authentication request is there in plain sight. Usernames. Domains. Full email addresses. If this file leaks, half your company is exposed.
Masking email addresses in logs for RADIUS isn’t optional anymore — it’s a mandate for security, compliance, and privacy. RADIUS logs often store sensitive identifiers in User-Name attributes. Without masking, these identifiers can be scraped, indexed, and misused.
The right approach starts at the source. When your RADIUS server processes an Access-Request, intercept the User-Name before it reaches persistent storage. Use regular expressions to replace the local-part with a placeholder. For example:
user@example.com -> *****@example.com
Do this before logging. Not after. Masking at write-time ensures raw addresses never touch disk.
In FreeRADIUS, use unlang policy in authorize to rewrite User-Name before any linelog or detail modules run:
if ("%{User-Name}"=~ /^(.*?)@(.*)$/) {
update request {
&User-Name := "*****@%{2}"
}
}
In commercial RADIUS implementations, look for policy hooks or log filters. Some systems provide a log-format option that can run transformations inline. Keep backups masked too — an old unmasked archive is still a breach.
Masking protects against internal misuse and external compromise. It helps satisfy GDPR, CCPA, and ISO 27001 controls regarding personal data. It also reduces the blast radius of any intrusion.
Do not truncate only part of the domain. Attackers can still deanonymize small user pools with partial data. Mask aggressively and consistently. Test your regex against edge cases such as uppercase input, aliases, and malformed addresses.
Once masking’s in place, monitor your logs for compliance. Automate checks to confirm no unmasked emails slip through after updates. Treat this as part of your CI/CD pipeline.
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