Active Directory Trusts

๐Ÿ”’ Secure Bits ๐Ÿ’ก
๐——๐—ผ ๐˜†๐—ผ๐˜‚ ๐˜‚๐˜€๐—ฒ ๐—ง๐—ฟ๐˜‚๐˜€๐˜๐˜€ ๐—ถ๐—ป ๐—”๐—ฐ๐˜๐—ถ๐˜ƒ๐—ฒ ๐——๐—ถ๐—ฟ๐—ฒ๐—ฐ๐˜๐—ผ๐—ฟ๐˜†?

There is no such thing as a security boundary between trusted domains.
Once you trust another AD, their problems become your problems.
One compromise can cascade across environmentsโ€”no matter the trust direction.

โš ๏ธ ๐—–๐—ฎ๐—ป ๐˜†๐—ผ๐˜‚ ๐—ฟ๐—ฒ๐—ฎ๐—น๐—น๐˜† ๐˜ƒ๐—ผ๐˜‚๐—ฐ๐—ต ๐—ณ๐—ผ๐—ฟ ๐˜๐—ต๐—ฒ๐—ถ๐—ฟ ๐˜€๐—ฒ๐—ฐ๐˜‚๐—ฟ๐—ถ๐˜๐˜†?

I generally donโ€™t recommend using trustsโ€”
โ€ฆbut in the real world, business needs often override security advice.

If you must use them, ๐—บ๐—ฎ๐—ธ๐—ฒ ๐˜€๐˜‚๐—ฟ๐—ฒ ๐˜†๐—ผ๐˜‚ ๐—ฑ๐—ผ ๐—ถ๐˜ ๐—ฟ๐—ถ๐—ด๐—ต๐˜:
โœ… Use the right type of trust โ€“ aim for smaller exposure (Forest vs External)
โœ… Enable Selective Authentication โ€“ Limit who can authenticate where across the trust.
โœ… Force Kerberos AES โ€“ Avoid falling back to weaker methods.
โœ… Check SID Filtering โ€“ Itโ€™s often disabled from past migrations and never re-enabled.

๐Ÿงช Scan with Get-ADTrust/nltest + netdom or use my transparent PowerShell tool โ€“ ADProbe โ€“ to simplify the check. https://horizon-secured.com/tools/

๐Ÿšซ And noโ€”child domains are not a security boundary – I see this too often.
Anyone from a child can become Enterprise Admin with enough access. If youโ€™re doing it for separation, consider OUs and delegation instead.

Do you use AD trusts in your environment? Whatโ€™s your use case?