If these are like the ones I've seen, they're mostly (or all) coming from the "Tide" proxy servers at Microsoft. As such they're fairly easy to block based on their REMOTE_ADDR, REMOTE_HOST, and VIA headers.
You should be able to confirm this by reviewing your server access log file, and searching for the 'spammy' terms.
Msg#: 3389310 posted 12:43 am on Jul 10, 2007 (gmt 0)
Yes, that IP address resolves to tide526.microsoft.com
I don't know what these people (or robots) are up to --or whether blocking these accesses will actually accomplish anything-- but if you're on Apache, something like this in .htaccess would return a 403-Forbidden response for these requests:
This second version, based on the tide.microsoft.com hostnames, eliminates the possible need to maintain the IP address "list" for the REMOTE_ADDR check in the first code snippet.
In the second version, the RewriteCond examining the referrer isn't strictly necessary, but I included it to limit the number of reverse DNS lookups, which are by nature 'expensive' in terms of CPU cycles and waiting server threads. You can make it even more specific by including the search terms that you find in the requests to your server, as in: