This just started happening. When a new commenter visits my site, they are taken to a 403 error that reads:
This server has detected suspicious activity and is rejecting your request. Possible reasons for rejecting your connection include:
* Connection originates from an Open Proxy
* Referer contains a blacklisted phrase or URI
* Posted comment contains a blacklisted phrase or URI
Due to the security and spam problems associated with open proxies, this site does not accept connections from them. If you feel that you have received this message erroneously, please contact your network administrators and inform them of this issue. To determine if your connection is via an open proxy, check the Blitzed Open Proxy Monitor List.
If you feel that you have received this message erroneously, you can contact the administrator of this web server at: lifeinchoate (at) gmail (dot) com.
The new commenter can try to make a new comment but will continue to get that (however, their comments do come through to my moderation panel).
I haven't done any upgrades to my site since 2.3 came out. I haven't added any plugins. I don't have the bad behavior plugin.
I didn't see any other topics on this specific issue.