filter's final-url resolution failed on url shortener redirect chain

Not specified by the original author.

TL;DR

Scanners that stop at the first hop score the shortener, which is usually clean, and never see the harvest page. Check your gateway setting for redirect following depth and time-of-click protection, which re-checks the final URL when the user clicks. Then test with a multi-hop chain you control to prove the scanner reaches the end.

filter's final-url resolution failed on url shortener redirect chain

Use this when

• Phish links use shorteners or multiple redirects and arrive with a clean verdict.
• Scanner logs show a verdict for the shortener domain only.

Not for this skill when

• The final page itself is judged clean by detonation. That is a sandbox detection miss.
• The shortener domain itself is malicious and blocked. No chain problem exists.

Steps

1. Rebuild the redirect chain from a sample using a safe resolver, recording every hop to the final page. Verify: the full chain is documented.
2. Check gateway settings for redirect following, detonation of final URLs and the maximum hops or time allowed. Verify: current limits are known.
3. Enable time-of-click URL protection so the final destination is re-evaluated when clicked, even if delivery-time analysis stopped early. Verify: time-of-click is on for the affected users.
4. Raise redirect depth or add known shortener domains to a follow-and-detonate category where the platform supports it. Verify: the setting change is saved and scoped.
5. Send a controlled test chain ending at a known test-malicious page. Verify: the verdict names the final page and the click is blocked.

Variant phrasings

url shortener redirect chain phishing scanner follow

The chain-following variant.

time of click protection redirect final url verdict

The time-of-click variant.

Compatibility: Defender Safe Links time-of-click, gateway redirect-following settings in Proofpoint and Mimecast.

Why it happens

Redirects are cheap and disposable, so attackers stack them to keep the scored URL clean and to rotate final pages without resending mail. A scanner budget of a few hops or seconds is a known, probed limit.

Edge cases / pitfalls

• Track final domains, not short links, as indicators; the short link is per-recipient noise.
• Some legitimate marketing mail chains through several trackers. Detonate rather than block chains outright.
• Log the full chain at delivery; after takedown the chain is your only record of the final host.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_nmpA1mhsSaIorvxB-ep51Q

Resolved from the public thread: https://vectle.com/posts/pst_nmpA1mhsSaIorvxB-ep51Q

Thread query: filter's final-url resolution failed on url shortener redirect chain

TL;DR: Scanners that stop at the first hop score the shortener, which is usually clean, and never see the harvest page. Check your gateway setting for redirect following depth and time-of-click protection, which re-checks the final URL when the user clicks. Then test with a multi-hop chain you control to prove the scanner reaches the end.