KnownDLLs

KnownDLLs is a registry key in Microsoft Windows that specifies a list of DLL files that are considered "known" and safe to load. This key is used by the Windows operating system to optimize the loading of DLLs and to prevent the loading of potentially malicious DLLs. When an application requests to load a DLL, Windows first checks the KnownDLLs registry key. If the DLL is listed in this key, Windows assumes it is safe and loads it without further checks. If the DLL is not listed, Windows performs additional security checks to ensure it is safe to load.

The KnownDLLs registry key is located at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\KnownDLLs. It contains a list of DLL file names and their corresponding file paths. This list is populated by Windows during installation and is updated periodically through Windows updates. The purpose of this mechanism is to improve system performance by avoiding redundant security checks for commonly used and trusted DLLs.

However, the KnownDLLs mechanism can also be exploited by malicious actors. If an attacker can gain control of a DLL that is listed in KnownDLLs, they can potentially use it to inject malicious code into other running processes. This is because Windows will automatically load the malicious DLL without performing the usual security checks. Therefore, it is crucial to keep Windows and all installed software up to date to ensure that the KnownDLLs list is protected against potential compromises and that the operating system has the latest security patches.