Anyone have a good link for reference [1] in the PDF? I tried navigating to it but get a 404. Potentially related URLs [2][3] I found also 404? Hm.

[1] https://www.nsa.gov/cybersecurity-guidance [2] https://www.nsa.gov/What-We-Do/Cybersecurity/Advisories-Tech... [3] https://www.nsa.gov/what-we-do/cybersecurity/