I would suggest taking a look at the CIS Benchmarks for Windows and SQL Server. These are great guidelines that can help you harden your environment: https://learn.cisecurity.org/benchmarks
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Georg Thomas | CISSP, CISM, CEH, GIAC, MCSE (Security), MVP Twitter
@georgathomas This forum post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.