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When I check the logs Googlebot/2.1 is at the top of the user agents list.
However, this much bandwidth seems excessive for crawling.
600mb is not a lot of traffic - surely this wasn't even close to your reseller quota.
I'd unban everything and just let them feed - let them suck down as much as they can take if you'll benefit - bandwidth is relatively cheap.
If it is becoming a problem, report it to email@example.com, and if necessary add some robots meta tags to exclude the bot from areas where it has become trapped.