Nah, this isn't a matter of someone naming a file with loads of keywords... these spam files have the exact string I searched for in the filename, nothing else.

If I was searching for, say, Nirvana Live Bootleg, the files in question do not return:

this is a spam file (nirvana live bootleg britney spears xxx porn whatever other tags spammers use mp3 blah blah)

but instead:

this is a spam file (Nirvana Live Bootleg)

Ok, so I'm thinking some spammer got lucky with that tagging... so I search for Nirvana Live Bootleg Germany 1993 and get:

this is a spam file (Nirvana Live Bootleg Germany 1993)

Same exact file, but with my new search query inserted. I could see if I was using narrow searches (ie, Nirvana), but I'm searching for pretty specific stuff and hitting these. I could also see if the file had a ton of keywords in it, but they don't... just the exact thing I searched for, nothing else.

(I don't know if these particular strings bring back these spam files... just used random stuff to clarify my point).