Our ExchangeDefender network on 188.8.131.52/24 network sustained an extended DDoS attack since approximately 7 AM EST. While the attack was addressed nearly immediately, due to the failover routing in ExchangeDefender, this network was removed from the scanning grid and deactivated. At this point, we are reactivating it and all traffic patterns should be back to normal.
Users should not have have been able to notice any interruption as the network is load balanced across other data centers. There may have been some limited delays in email delivery for any messages that were in-scanning when the DDoS started.