credential phishing" url flagged by users but missed by gateway

TL;DR

When users find it first, treat the first report as the detection system: extract the real URL from the message, not the screenshot, check it in a safe analysis environment, block it at the tenant, and search for every other recipient. Gateways miss novel URLs because reputation is empty at first send, so your response speed, not the feed, decides the exposure window.

"credential phishing" url flagged by users but missed by gateway

Use this when

• One or more users reported a credential phishing link that was delivered clean.
• A URL from a report has no verdict in gateway logs.

Not for this skill when

• The URL is already blocked and users saw the block page. That is the control working.
• The link is a legitimate service being abused for hosting. Block the full URL path, not the whole service domain, where possible.

Steps

1. From the reported message headers and body, extract the href target behind the display text and any redirect chain. Verify: the final credential page URL is identified.
2. Analyse the URL in an isolated tool such as urlscan or your sandbox, never from a production workstation browser. Verify: screenshots and page behaviour confirm or clear the credential harvest suspicion.
3. If confirmed, block the URL and domain in the tenant list and submit to the gateway vendor for global detection. Verify: the block is active and the submission is acknowledged.
4. Search and purge: find all messages containing the URL or its redirector and remove delivered copies. Verify: the purge count matches the search count.
5. Check for engagement: use audit and proxy logs to see whether anyone submitted credentials, and trigger password resets for anyone who did. Verify: affected users are listed and resets are forced.

Variant phrasings

users reported phishing url gateway missed response

The incident response variant.

extract real url behind link text phishing triage

The extraction variant.

Compatibility: Defender tenant allow block list and submissions, urlscan.io and gateway URL analysis tools.

Why it happens

Reputation feeds are built from reports, so a genuinely new campaign URL has no score anywhere at first delivery. The gateway behaved as designed; the gap is that the tenant had no fast local response loop from user report to block.

Edge cases / pitfalls

• Teach users to use the report button rather than forwarding, which preserves headers and the original URL encoding.
• Redirector URLs rot quickly. Record final domains and page hashes as durable indicators.
• If credentials were submitted, the incident is an account compromise response, not just a mail problem.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_fwnQ8x91TKbnnVnQAGlqvg