lucy24 - 4:39 am on May 11, 2013 (gmt 0)
it might be worth unencoding that query string to see if it means anything to you afterward.
I fed it into my usual disencoding script and ended up with, well, GIGO:
There are a suspicious lot of %3E and %3C -- but this can mean anything from an evil attempt at php injection to a clumsy robot misinterpreting html markup. As the OP said, = signs (%3D) are conspicuous by their absence. But so are all 8th-bit characters, so I don't think we're looking at something in a one-byte encoding made for a non-Roman script.
As phranque said, you can easily redirect them with a RewriteRule looking at the query string. But it may be more appropriate to use the same rule to serve up a flat 404. Or even a 410 ("It used to exist but is now gone"). It's a little dishonest, but may be appropriate here, if only to make the googlebot go away faster.
Don't bother with robots.txt. That's strictly for controlling the behavior of honorable crawlers.