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In Microsoft Office Excel, you can change the macro security settings to control which macros run and under what circumstances when you open a workbook. For example, you might allow macros to run based on whether they are digitally signed by a trusted developer.

For more information about macro security settings in Microsoft Office documents, see Enable or disable macros in Office documents.

• Macro security settings and their effects

• Change macro security settings

• Using digital signatures

Macro security settings and their effects

The following list summarizes the various macro security settings. Under all settings, if antivirus software that works with 2007 Microsoft Office system is installed and the workbook contains macros, the workbook is scanned for known viruses before it is opened.

• Disable all macros without notification Click this option if you don't trust macros. All macros in documents and security alerts about macros are disabled. If there are documents that contain unsigned macros that you do trust, you can put those documents into a trusted location. Documents in trusted locations are allowed to run without being checked by the Trust Center security system.
• Disable all macros with notification This is the default setting. Click this option if you want macros to be disabled, but you want to get security alerts if there are macros present. This way, you can choose when to enable those macros on a case by case basis.
• Disable all macros except digitally signed macros This setting is the same as the Disable all macros with notification option, except that if the macro is digitally signed by a trusted publisher, the macro can run if you have already trusted the publisher. If you have not trusted the publisher, you are notified. That way, you can choose to enable those signed macros or trust the publisher. All unsigned macros are disabled without notification.
• Enable all macros (not recommended, potentially dangerous code can run) Click this option to allow all macros to run. Using this setting makes your computer vulnerable to potentially malicious code and is not recommended.
• Trust access to the VBA project object model  This setting is for developers and is used to deliberately lock out or allow programmatic access to the VBA object model from any Automation client. In other words, it provides a security option for code that is written to automate an Office program and programmatically manipulate the Microsoft Visual Basic for Applications (VBA) environment and object model. This is a per user and per application setting, and denies access by default. This security option makes it more difficult for unauthorized programs to build "self-replicating" code that can harm end-user systems. For any Automation client to be able to access the VBA object model programmatically, the user running the code must explicitly grant access. To turn on access, select the check box.

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Change macro security settings

You can change macro security settings in the Trust Center, unless a system administrator in your organization has changed the default settings to prevent you from changing the settings.

1. On the Developer tab, in the Code group, click Macro Security.

    Tip   If the Developer tab is not displayed, click the Microsoft Office Button , click Excel Options, and then in the Popular category, under Top options for working with Excel, click Show Developer tab in the Ribbon.

2. In the Macro Settings category, under Macro Settings, click the option that you want.

    Note   Any changes that you make in the Macro Settings category in Excel apply only to Excel and do not affect any other Microsoft Office program.

 Tip   You can also access the Trust Center in the Excel Options dialog box. Click the Microsoft Office Button , and then click Excel Options. In the Trust Center category, click Trust Center Settings, and then click the Macro Settings category.

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Using digital signatures

The 2007 Office release uses Microsoft Authenticode technology to enable macro creators to digitally sign (digital signature: An electronic, encryption-based, secure stamp of authentication on a macro or document. This signature confirms that the macro or document originated from the signer and has not been altered.) a file or a macro project (macro project: A collection of components, including forms, code, and class modules, that make up a macro. Macro projects created in Microsoft Visual Basic for Applications can be included in add-ins and in most Microsoft Office programs.). The certificate that is used to create this signature confirms that the macro or document originated from the signer, and the signature confirms that the macro or document has not been altered.

After you install your digital certificate (digital certificate: Attachment for a file, macro project, or e-mail message that vouches for authenticity, provides secure encryption, or supplies a verifiable signature. To digitally sign macro projects, you must install a digital certificate.), you can sign files and macro projects.

Obtaining a digital certificate for signing

You can obtain a digital certificate from a commercial certificate authority (CA) (certificate authority (CA): A commercial organization that issues digital certificates, keeps track of who is assigned to a certificate, signs certificates to verify their validity, and tracks which certificates are revoked or expired.), or from your internal security administrator or information technology (IT) professional.

To learn more about certificate authorities that offer services for Microsoft products, see the list of Microsoft Root Certificate Program Members.

Creating your own digital certificate for self-signing

You can also create your own self-signing certificate by using the Selfcert.exe tool.

 Note   Because a digital certificate that you create isn't issued by a formal certificate authority, macro projects that are signed by using such a certificate are referred to as self-signed projects. Microsoft Office trusts a self-signed certificate only on a computer that has that certificate in your Personal Certificates store.

For more information about how to digitally sign a macro, see Digitally sign a macro project.

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