1. A security controller apparatus for providing messaging services on a data exchange layer (DXL), comprising: a network interface; a DXL services engine operable for providing an application programming interface (API) for connecting to a DXL enterprise service bus (ESB) via the network interface; and a domain security engine operable for: subscribing to a DXL security topic; detecting a security event via the DXL ESB; and publishing a DXL security message via the DXL ESB configured for acting on the security event.