I tried it twice. Had an audio search open with several spam results that couldn't be banned by filename pattern without false positives (filename didn't contain NEW MIX or similar added material, just search terms, numbers, etc., and extension that legitimate hit could have).
Right click, copy URI, extract just the urn:sha1:GHSKFKGKGKLGL part, paste into new "Match Any" content-ban security rule. No effect.
Right click, find this file, hit stop in new search, copy urn:sha1:BLAHBLAH from search field, paste into new "Match Any" content-ban security rule. No effect.
Both bogus hits still in search results; show 0 hits in security tab.
What gives here?