Audit of Disappearing Call Logs

What are Disappearing Call Logs?

Call Logs, also called Call Detail Records (CDRs), are subscriber records of call, text, and data usage. Most telecoms keep these records for months to years, building detailed profiles about your patterns and habits, selling them to ad networks and data brokers, and in some cases handing them over to the government.

At Cape, we delete call logs after just 1 day, and only use them for billing and spam detection purposes. You can read more about our Disappearing Call Logs feature on 404 Media or our blog.

The Trail of Bits Attestation

The cybersecurity research firm Trail of Bits conducted an audit of our Disappearing Call Logs feature in May and July of 2026.

You can also find the attestation on Trail of Bit's GitHub.

Audit Findings

Prior to the audit, Cape stored daily totals in pseudo-anonymous form. The auditor flagged that an internal adversary with access to the proper databases can associate these totals to individual subscribers by linking the psuedo-anonymous identifier to static identifiers. Cape explored anonymization techniques of daily totals with Trail of Bits including HMAC key rotation and secure enclaves but determined both are susceptible to an internal adversary with administrator access (that can deploy code changes), which is the same threat model as the psuedo-anonymous approach. As a remediation to this finding, Cape deletes daily totals older than 60 days and we corrected our feature description to remove reference to anonymous storage.