Our free MITM Detector analyzes TLS connections for signs of Man-in-the-Middle attacks. It checks certificate anomalies, unexpected certificate authorities, certificate pinning mismatches, and suspicious TLS handshake patterns that may indicate interception.
How to Use
Enter the domain name you want to test for MITM indicators
Click "Run" to perform the MITM detection analysis
Review the results for any suspicious certificate or handshake anomalies
Use Cases
•Enterprise security monitoring for unauthorized certificate interception
•Verifying certificate pinning implementations are working correctly
•Detecting rogue certificate authorities in your TLS trust chain
Frequently Asked Questions
A Man-in-the-Middle (MITM) attack occurs when an attacker secretly intercepts and possibly alters the communication between two parties. In TLS, this typically involves presenting a fake certificate that the target trusts, allowing the attacker to decrypt and read all traffic.
Use certificate pinning, enable HTTP Strict Transport Security (HSTS), implement Certificate Transparency monitoring, and ensure your certificate validation logic is robust. Regular scanning with MITM detection tools helps identify potential issues early.
Unexpected certificate authorities, certificates issued to different domains, sudden changes in certificate fingerprints, mismatched Subject Public Key Info, and certificates signed by internal enterprise CA servers when connecting to external sites are common MITM indicators.
No, and this is the single most common reason this check produces a finding on an otherwise healthy site. Traffic inspection products sit between employees and the internet and re-encrypt with their own certificate, so they are technically indistinguishable from an interception attack. The difference is intent and consent. The practical response is to identify it, confirm it is deliberate, and then decide what to do — commonly to trust the inspection authority on managed devices only, so that unmanaged machines are still checked.
The certificate itself, mostly. An interceptor has to produce a certificate, and it will often differ from what your server should be serving: a different issuer, a much longer validity period than modern authorities issue, or a subject that does not match the hostname. Behaviour tells too — a protocol version or cipher that no real client would offer, or a handshake that takes noticeably longer than the same connection from elsewhere. Header checks alone miss all of these.
Yes. An intermediary controlling the path can present a certificate from any issuer it likes, including one that looks entirely ordinary, and it can strip any identifying header. That is the honest limitation of every remote check. What catches a determined attacker is comparing the certificate you see against the one you know your server holds, and checking the same host from a network you control — a discrepancy between those two views is what a hiding interception cannot produce.
Because legitimate software also re-encrypts. Corporate inspection, some endpoint protection products, and a few ISPs doing error-page injection all present certificates that are not the site's own. The distinguishing questions are whether you deployed it, whether it is expected on that network, and whether the certificate is trusted on the device. A certificate appearing on a network you do not control, that nobody installed, is the case worth escalating.
Capture the certificate details first, because they are the evidence and they will not be there later. Then compare against what your server should be presenting, and test the same host from a network outside the one that showed the finding. If it reproduces everywhere, treat it as a compromise and rotate your keys. If it appears only on one network, you have found the path and the decision is whether that path is authorised.
What the Detection Looks For
An interception that re-encrypts your traffic has to present a certificate of its own, and that certificate is often unlike the one your server was configured with.
1Complete the handshake and read the certificate that was actually presented, which is the certificate an interceptor had to generate rather than forward.
2Look for characteristics of interception tooling, including issuers associated with enterprise security inspection products. These are legitimate deployments, which is why they are reported as a potential finding rather than an attack.
3Report either a potential interception or a clean result, and say which indicators were responsible.
A clean result means no indicator was found, not that the connection was certainly private. A sophisticated interception removes every fingerprint it can, and the definitive answer comes from comparing this certificate against the one your server should be serving.
Tips & Best Practices
•Monitor for MITM attack indicators on your domains
•Use certificate transparency for MITM detection
•Implement certificate pinning for critical applications
•Investigate any unexpected certificate changes immediately
Technical Details
Detection: Man-in-the-middle attack detection methods Indicators: Certificate anomalies, unexpected issuers, chain issues Protection: Certificate pinning and CT monitoring Output: MITM detection status with recommendations
