DirectX is a technology used by multimedia programs running on your system. The DirectX Diagnostic tool (DXdiag) helps you troubleshoot DirectX related issues such as, checking digital signatures for your video card drivers. It also checks whether a driver has passed the Microsoft’s Windows Hardware Quality Labs (WHQL) tests. But most importantly, it helps find problems with games or movies that cannot run properly. The first time you run the DXdiag tool you are asked whether you want to check if your drivers are digitally signed and that the tool may connect to the Internet but no personal data is collected.
Make sure that you select the Check for WHQL digital signatures option in order to test for signed drivers. That is, digitally signed drivers have been tested by the Microsoft Windows Hardware Quality Lab for DirectX compatibility. It is recommended, to update a driver that is flagged as unsigned.