Anatomy of a Breach

Anatomy of a Breach: Comodo — The Iranian Hacker Who Forged the Internet's Trust

> series: anatomy_of_a_breach —— part: 027 —— target: comodo_ca —— fake_certs_for: google_yahoo_skype —— attacker: iranian_hacker<span class="cursor-blink">_</span>_

Hedgehog Security 31 March 2011 12 min read

Fake certificates for Google. Yahoo. Skype. The padlock lied.

On 15 March 2011, Comodo, one of the world's largest certificate authorities, disclosed that an attacker had compromised one of its registration authority (RA) partners — a reseller authorised to validate and issue SSL certificates on Comodo's behalf — and used the access to fraudulently issue nine SSL certificates for high-value domains including mail.google.com, login.yahoo.com, login.skype.com, addons.mozilla.org, and login.live.com (Microsoft).

A fraudulent SSL certificate for mail.google.com, combined with DNS manipulation or network-level interception, would allow an attacker to perform a man-in-the-middle attack on Gmail traffic — intercepting emails, passwords, and attachments while the victim's browser displayed the trusted padlock icon. The attacker, who later identified himself online as a 21-year-old Iranian claiming patriotic motivation, stated his objective was to enable surveillance of Iranian dissidents' communications — the same motivation behind elements of Operation Aurora.


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The internet's trust model has a single point of failure.

The HTTPS padlock icon — the indicator that tells users their connection is secure — depends on the certificate authority system. Any CA trusted by the browser can issue a certificate for any domain. If a CA is compromised, an attacker can issue certificates that browsers will accept as legitimate. The Comodo breach demonstrated that the CA system's weakest link is not the cryptography — it is the human and organisational processes at hundreds of CAs and their reseller partners worldwide.

Any CA Can Issue for Any Domain
The fundamental design flaw in the CA system is that every trusted CA can issue certificates for every domain. Comodo's Italian RA partner — a small company with limited security — could issue certificates for Google. This design has since been partially addressed by Certificate Transparency logs, CAA DNS records, and technologies our <a href="/penetration-testing/web-application">web application testing</a> verifies are correctly implemented.
Nation-State Surveillance Enabler
A fraudulent certificate for Gmail enables surveillance at national scale — any government that controls its country's DNS or network routing can intercept all Gmail traffic for its citizens. This was the stated motivation of the Comodo attacker. For organisations handling sensitive communications, our <a href="/penetration-testing/infrastructure">infrastructure testing</a> includes TLS configuration review and certificate pinning assessment.
Supply Chain Trust Again
Comodo itself was not directly compromised — its RA partner was. The supply chain weakness is the same pattern we see repeatedly: the primary vendor's security depends on the weakest link in its partner ecosystem. <a href="/cyber-essentials">Cyber Essentials</a> helps organisations assess their own supply chain, and our <a href="/blog/sector-under-the-microscope-professional-services">professional services analysis</a> examines third-party trust risks.
Certificate Transparency Is Now Essential
Post-Comodo and <a href="/blog/anatomy-of-a-breach-diginotar-ca">DigiNotar</a>, Certificate Transparency (CT) logs were developed to provide public, auditable records of every certificate issued. <a href="https://www.socinabox.co.uk">SOC in a Box</a> can monitor CT logs for unauthorised certificates issued for your domains — detecting rogue certificates before they are used in attacks.

Certificate security controls that matter.

For organisations that depend on HTTPS (which is every organisation), the Comodo breach established that trusting the CA system blindly is insufficient. Proactive certificate security includes implementing CAA DNS records (specifying which CAs may issue certificates for your domain), monitoring Certificate Transparency logs for unauthorised issuance, deploying HSTS (HTTP Strict Transport Security) to prevent downgrade attacks, and including TLS configuration in your web application penetration testing scope.

SOC in a Box provides continuous monitoring including CT log surveillance. Our infrastructure testing assesses your TLS configuration, certificate management, and HTTPS deployment. Cyber Essentials establishes baseline security configuration. And UK Cyber Defence provides incident response when certificate-related attacks are detected.


Could someone issue a fake certificate for your domain?

Our <a href="/penetration-testing/web-application">web application testing</a> includes TLS configuration review and certificate security assessment. <a href="https://www.socinabox.co.uk">SOC in a Box</a> monitors Certificate Transparency logs for unauthorised certificates. Because the padlock only means something if the certificate behind it is genuine.

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