How to Use the File Signature Verification

File Signature Verification (Sigverif.exe) detects signed files and allows you to

• View the certificates of signed files to verify that the file has not been tampered with after being certified.
• Search for signed files.
• Search for unsigned files.

Note Unsigned or altered drivers cannot be installed on x64-based versions of Windows.

Driver signing is a multistage process in which device drivers are verified. For a driver to earn this certification, it must pass a series of compatibility tests administered by the Windows Hardware Quality Labs (WHQL). Because of stringent WHQL standards, using signed drivers typically results in a more stable system. When troubleshooting a problem that might be caused by a driver, you might choose to remove unsigned drivers to eliminate the possibility that the unsigned driver is causing the problem. Although most unsigned drivers will not cause problems, they have not been verified by Microsoft and therefore have a higher risk of causing problems than signed drivers. Microsoft digitally signs drivers that pass the WHQL tests, and Windows performs signature detection for device categories such as:

• Keyboards
• Hard disk controllers
• Modems
• Mouse devices
• Multimedia devices
• Network adapters
• Printers
• SCSI adapters
• Smart card readers
• Video adapters

A Microsoft Corporation digital signature indicates that a driver file is an original, unaltered system file that Microsoft has approved for use with Windows. Windows can warn or prevent users from installing unsigned drivers. If a driver is not digitally signed, the user receives a message that requests confirmation to continue. Microsoft digitally signs all drivers included with Windows or distributed by Windows Update. When you download updated drivers from a manufacturer's Web page, always select drivers that are signed by Microsoft.

The following tools are useful for troubleshooting problems caused by unsigned files:

• File Signature Verification
• Device Manager
• Driver Verifier Manager

To identify unsigned drivers, follow these steps:

1. Click Start and then type Sigverif. Press Enter.
2. In the File Signature Verification window, click Start.
3. After several minutes, the Signature Verification Results page displays unsigned drivers. Unsigned drivers can be reliable, but they have not undergone the same testing that is required of signed drivers. If you are experiencing reliability problems, you should replace unsigned drivers with signed versions from Microsoft.
4. Click Close to return to the File Signature Verification window.
5. Click Close again.