None of the compliance regulations (e.g. PCI, HIPAA, GLBA, Basel II, FERPA, or SOX) forbid Windows Authentication mode
Actually, it's recommended not to use supplied system and other security parameters on SQL Server. Instead of using the mixed mode (enables both Windows authentication and SQL Server authentication), use the Windows authentication only. It utilizes the Windows password policy for accessing SQL Server. This enables checking the password history, password minimum length, and password minimum and maximum life. The most important Windows password policy characteristics is the login lockout - if a login continuously fails for a specified number of times
When it comes to SQL Server authentication brute-force attack vulnerability, the situation is not so favorable. SQL Server Authentication has no features that allow detecting when the system is under a brute-force attack. Moreover, SQL Server is very responsive when it comes to validating the SQL Server authentication credentials. It can easily handle repeated, aggressive, brute-force login attempts without negative overall performance that might indicate such attacks. This means that the SQL Server Authentication is a perfect target for password cracking via brute-force attacks
Also, brute-force methods are evolving with each newly introduced encryption and password complexity method. For example, attackers that use rainbow tables (the pre-computed tables for reversing the cryptographic hash values for every possible combination of characters) can easily and quickly crack any hashed password