AppLocker DLL Rules Performance Impact

Question

Hi team,

A security engineer wants to expand our AppLocker policy to audit and control not just .exe and .msi files, but every single DLL loaded by the operating system. What specific performance degradation warnings does Microsoft issue regarding DLL rule enforcement, and how does it affect disk I/O on standard office workstations?

Thanks

Sahil

Answer 1

Hi Sahil,

Microsoft’s concern is that turning on AppLocker for DLLs can slow things down quite a bit. Every time a program runs, Windows loads a large number of small files called DLLs, and AppLocker would need to check each one against the policy.

Because this happens constantly, it creates a lot of extra work in the background, especially hitting the disk repeatedly. On a normal office PC, that can show up as slower app launches, longer logon times, and general sluggishness.

That’s why Microsoft recommends avoiding DLL enforcement unless it’s really necessary, and testing it first in audit mode. In simple terms, it adds a heavy “inspection step” to almost everything your system does.

So while it improves control, it often comes at the cost of noticeable performance impact on everyday use.Harry.