Invalid SQL (from search.php)
 

I receive like 10 notifications everyday from my forums saying:
Code:
Invalid SQL:
SELECT threadid FROM vb_thread AS thread
WHERE threadid IN(here goes a list of the 500,000 threads IDs!)
ORDER BY lastpost DESC;
Script : http://********.com/search.php?do=process
My question is: what type of search generates this query? I need to disable it. How?