PBBans (an anti-cheat community offering full support for PunkBuster enabled games) is currently disabled do to a DoS attack. Current plans are to find a new host and move their server to a difference location (as a result of overwhelming request to keep it running from supporters). Initially they were planning to close their doors for good.
Currently there is no ETA of when their service will be back online. There is a lot more to this story then this. From what I've read (around the web) is that other anti cheating sites were hit as well.
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