Intelligence Community Directive, Number 502, Integrated Defense of the Intelligence Community Information Environment, March 11, 2011 [open pdf - 1MB]
"This Directive establishes policy on the integrated defense of the information environment for the Intelligence Community (IC). Integrated defense includes oversight, management, operations, and response activities within the IC, and in coordination with United States Government departments or agencies and other entities external to the IC. Integrated defense is essential to both information sharing and to the protection of sources and methods from unauthorized disclosure."
Intelligence Community Directive 502; ICD 502