Kerberos Authentication Policy Silos

๐Ÿ”’ Secure Bits ๐Ÿ’ก
๐—”๐˜‚๐˜๐—ต๐—ฒ๐—ป๐˜๐—ถ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป ๐—ฃ๐—ผ๐—น๐—ถ๐—ฐ๐˜† ๐—ฆ๐—ถ๐—น๐—ผ๐˜€. ๐—ช๐—ต๐˜†?

So, by now you know how Kerberos works, you understand Kerberoasting, and youโ€™ve seen how Authentication Policies can help.

Letโ€™s talk about the next layer: ๐—”๐˜‚๐˜๐—ต๐—ฒ๐—ป๐˜๐—ถ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป ๐—ฃ๐—ผ๐—น๐—ถ๐—ฐ๐˜† ๐—ฆ๐—ถ๐—น๐—ผ๐˜€.

Silos are essentially ๐—ฐ๐—ผ๐—ป๐˜๐—ฎ๐—ถ๐—ป๐—ฒ๐—ฟ๐˜€ ๐—ณ๐—ผ๐—ฟ ๐˜‚๐˜€๐—ฒ๐—ฟ, ๐—ฐ๐—ผ๐—บ๐—ฝ๐˜‚๐˜๐—ฒ๐—ฟ, ๐—ฎ๐—ป๐—ฑ ๐˜€๐—ฒ๐—ฟ๐˜ƒ๐—ถ๐—ฐ๐—ฒ ๐—ฎ๐—ฐ๐—ฐ๐—ผ๐˜‚๐—ป๐˜๐˜€. You link them to an Authentication Policy, and everyone inside follows the rules of that policy (or more policies).

Why not to use just the Authentication Policy ?
You ๐—ฐ๐—ฎ๐—ปโ€™๐˜ ๐—ฎ๐—ฝ๐—ฝ๐—น๐˜† ๐—ฎ๐—ป ๐—”๐˜‚๐˜๐—ต๐—ฒ๐—ป๐˜๐—ถ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป ๐—ฃ๐—ผ๐—น๐—ถ๐—ฐ๐˜† ๐˜๐—ผ ๐—ฎ ๐—ด๐—ฟ๐—ผ๐˜‚๐—ฝ. So the silo acts like your grouping mechanism. Thatโ€™s it. A workaround with a fancy name.

๐—ฆ๐—ผ, ๐—ต๐—ผ๐˜„ ๐—ฑ๐—ผ๐—ฒ๐˜€ ๐—ถ๐˜ ๐˜„๐—ผ๐—ฟ๐—ธ?
โœ… You create a Silo
โœ… You link your Authentication Policy to it
โœ… You add accounts manually
โœ… You must also assign the silo to each accountโ€™s Silo tab in ADAC (Active Directory Administrative Center).

Double assignment. Why? I have no idea. If you do, let me know.

๐—ง๐—ผ ๐˜€๐—ฒ๐˜ ๐˜๐—ต๐—ถ๐˜€ ๐˜‚๐—ฝ:
1๏ธโƒฃ Create the Authentication Policy
โ–ช๏ธ Skip assigning accounts for now
โ–ช๏ธ Define your conditions โ€” e.g., User.AuthenticationSilo Equals “T0-Silo”
โ–ช๏ธ Set rules for sign-on, ticket lifetimes, etc.
2๏ธโƒฃ Create the Silo
โ–ช๏ธ Add permitted accounts
โ–ช๏ธ Attach the Authentication Policy
3๏ธโƒฃ Assign the Silo to each account via ADAC

โš ๏ธ You may need to reboot your Domain Controllers afterward. I always did.

๐—œ๐˜€ ๐—ถ๐˜ ๐˜„๐—ผ๐—ฟ๐˜๐—ต ๐—ถ๐˜?
Sometimes. It brings structure and better control. But in many of my cases, it felt like an unnecessary step โ€” especially in simpler environments.

Have you used Authentication Policy Silos? Was it helpful, or just added complexity?