The following snippet is a urlRewrite rule to disable traffic from a crawler. Just replace crawleragent with the User Agent of the crawler. The crawler will be sent a 403 Forbidden Response.
<rule> <name>Disable Crawler</name> <from>^.*$</from> <condition name="user-agent">crawleragent</condition> <set type="status">403</set> <to>null</to> </rule>