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>