What document does DSS publish to clarify existing policy requirements in the NISPOM?

The Industrial Security Letter (ISL) is the document published by the Defense Security Service (DSS) to clarify existing policy requirements in the National Industrial Security Program Operating Manual (NISPOM). The ISL serves as a means of communication that conveys important updates, policy changes, and guidance relevant to the security practices for cleared contractors. By providing these clarifications, the ISL helps ensure that organizations remain compliant with the requirements set forth in the NISPOM and can adapt to any new or revised guidelines.

The other options do not serve the same specific purpose as the ISL. The Policy Review Notes are typically more focused on internal assessments and updates rather than clarifications of existing policy. The NISPOM Update Bulletin may present updates but does not have the same authoritative role in clarifying existing policy as the ISL. Meanwhile, the Security Guidelines Digest is more general guidance rather than a targeted clarification resource for NISPOM policy requirements. This distinction emphasizes the importance of the ISL in supporting entities in maintaining compliance with government security mandates.