There are differences between the old DIACAP (being phased out), DoD RMF for IT and NIST RMF. What is “DIACAP”? It stands for Department of Defense Information Assurance Certification & Accreditation Process and it is based on the old DoDI 8510.01 and DoD 8500 documents. The process was designed to make absolutely sure federal systems have security on them.
With the constant exponential evolution of information technology this process has had to change to keep up with the times. DIACAP is being replaced with DoD Risk Management Framework for Information Technology (DoD RMF for IT). This process has more granularity, more detailed, more frequent and covers many new technology that was not covered by DIACAP. DoD RMF for IT is actually based fundamentally on NIST SP 800-37, Risk Management Framework.