NIST-SC-37 Out-of-band Channels

Employ the following out-of-band channels for the physical delivery or electronic transmission of [Assignment: information, system components, or devices] to [Assignment: individuals or systems]: [Assignment: out-of-band channels].

Out-of-band channels include local, non-network accesses to systems; network paths physically separate from network paths used for operational traffic; or non-electronic paths, such as the U.S. Postal Service. The use of out-of-band channels is contrasted with the use of in-band channels (i.e., the same channels) that carry routine operational traffic. Out-of-band channels do not have the same vulnerability or exposure as in-band channels. Therefore, the confidentiality, integrity, or availability compromises of in-band channels will not compromise or adversely affect the out-of-band channels. Organizations may employ out-of-band channels in the delivery or transmission of organizational items, including authenticators and credentials; cryptographic key management information; system and data backups; configuration management changes for hardware, firmware, or software; security updates; maintenance information; and malicious code protection updates. For example, cryptographic keys for encrypted files are delivered using a different channel than the file.

• T1071 Application Layer Protocol • T1071.001 Web Protocols • T1071.002 File Transfer Protocols • T1071.003 Mail Protocols • T1071.004 DNS • T1114 Email Collection • T1114.001 Local Email Collection • T1114.002 Remote Email Collection • T1114.003 Email Forwarding Rule • T1213 Data from Information Repositories • T1213.005 Messaging Applications • T1489 Service Stop