You can verify whether a Mac OS file or program that you've downloaded from the Internet is from the authorized sender and has not been modified by checking its digital signature using the Apple Verifier program (in the Security folder inside the Applications folder).

To verify the digital signature of a file or program:

•

Drag the item to the Apple Verifier icon. Show me the Apple Verifier program icon.

• If the file's signature is verified using the certificates in your keychain, you can choose to open the file or view the certificate by clicking a button in the Verification Results window. • If the file's signature is verified using certifcates that are not in your keychain, you can choose to trust that the certificates came from the person (or organization) they say they came from, and the certificate will be added to your keychain. If you choose not to trust it, the file remains on your hard disk. • If the signature is not verified, then either the file has been tampered with (possibly infected with a virus), or the file did not come from the source it says it did. You are at risk if you use the file. IMPORTANT: Before you trust a certificate, you should personally verify its digital "fingerprint" (the certificate's unique ID number that appears in the certificate window) by contacting the company directly. If you trust a certificate without verifying its ID, the security of files on your computer may be compromised.

Tip: For more information about items in the Verification Results or Trust window, open the Help menu and choose Show Balloons, then point to the item you want to learn about.

Related topic

Creating and adding items to a keychain