DSInternals is a comprehensive .NET library and PowerShell module for Active Directory security auditing, forensic analysis, and offline/in-place manipulation of AD databases. It provides the ability to extract password hashes (NT, LM, Kerberos), decrypt DPAPI backup keys, recover LAPS and gMSA secrets, parse FIDO2/Windows Hello key credentials, and query DNS zones and signing keys. The library supports multiple access modes: offline via ESENT/ISAM (ntds.dit), online via RPC replication (DRSR), LDAP/ADSI, and SAM/LSA native APIs. The PowerShell module exposes over 50 cmdlets organized into logical groups (ADDB, ADRepl, ADSI, LSA, SAM, Hash, Encryption). The codebase is heavily oriented toward reverse-engineering of Microsoft's internal AD structures and protocols, with extensive unit tests using real-world binary vectors. While the primary use case is security auditing (e.g., penetration testing, incident response), the library also provides utilities for password quality testing, domain controller recovery, and offline account modifications. The architecture is modular, with clear separation between common data models, data store access, replication, and PowerShell cmdlets, making it a robust toolkit for Windows domain administrators and security professionals.