看到美國總統行政辦公室發佈的「Moving the U.S. Government Toward Zero Trust Cybersecurity Principles」這個備忘錄，在講 Zero trust security model，算是讓其他聯邦單位可以依循的指引，從比較高的角度來說明聯邦政府對系統安全設計的方向。
裡面有提到「Phishing-resistant MFA」，一般的 MFA 無法防止 phishing (像是軟體 TOTP 類的 Google Authenticator 或是硬體式 TOTP 的 RSA SecurID，或是透過簡訊輸入收到的字串那種)，要能夠對抗 phishing 的應該只有 U2F 或是後續的 WebAuthn 這種有把網站位置也放進 protocol 的協定。
另外提到了 RBAC 與 ABAC 兩種設計，而且更偏好用 ABAC 得到更多彈性：
Currently, many authorization models in the Federal Government focus on role-based access control (RBAC), which relies on static pre-defined roles that are assigned to users and determine their permissions within an organization. A zero trust architecture should incorporate more granularly and dynamically defined permissions, as attribute-based access control (ABAC) is designed to do.
另外因為 zero trust 的設計，內部網路其實只能當作是一個傳輸媒介，不能當作是一個安全的傳輸層，任何的傳輸都需要有另外的驗證機制確保 CIA，所以從 DNS 的流量必須是透過 DNS over HTTPS 或是 DNS over TLS 的保護：
Agencies must resolve DNS queries using encrypted DNS wherever it is technically supported. This means that agency DNS resolvers must support standard encrypted DNS protocols (DNS-over-HTTPS or DNS-over-TLS), and must use them to communicate with upstream DNS resolvers.
任何 HTTP 傳輸都需要使用 HTTPS 保護，甚至是把 .gov 直接放進 HTTPS-only 清單 (應該是指 HSTS preload？)：
More generally, the .gov top-level domain has announced an intent to eventually preload the entirety of the .gov domain space as an HTTPS-only zone.
不過裡面也有提到 email 的 encryption 到目前為止沒有好的方法可以確保 encryption 的使用，尤其是跟外部的人溝通：
Unlike HTTP and DNS, there is not today a clear path forward for guaranteeing that Federal emails are encrypted in transit, particularly for emails with external parties.
然後提到安全漏洞的測試與回報機制也蠻有趣的，像是鼓勵外部測試：
In addition to their own testing programs, agencies must increase their reliance on external perspectives to identify vulnerabilities that internal staff may not identify
以及鼓勵安全回報的制度：
Public vulnerability disclosure programs, which allow security researchers and other members of the general public to report security issues safely, are used widely across the Federal Government and many private-sector industries. These programs are an invaluable accompaniment to existing internal security programs and operate as a reality check on an organization’s online security posture.
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