Security settings and Excel RealTimeData servers

Microsoft Office Excel provides the RTD worksheet function. The RTD worksheet function enables you to call an Automation server to retrieve real-time data. This article describes how RealTimeData servers are affected by security settings within Microsoft Excel.

A RealTimeData (RTD) server is invoked in Excel by using a worksheet formula that resembles the following: The behavior of the RTD server is governed by Excel security settings.

For Excel 2002 and Excel 2003

To examine or modify your security settings in Excel, on the Tools menu, click Macro, and select Security.

• When the security is set to High, the RTD server fails silently, and Excel displays #N/A in the worksheet cell.
• When the security is set to Medium, Excel displays a warning that the RTD server contains macros and asks the user whether to enable or disable them. If the macros are enabled, the RTD server runs correctly. If the macros are disabled, the RTD server fails silently and Excel displays #N/A in the worksheet cell.
• When the security is set to Low, the RTD server runs correctly without any security warnings.

Excel is designed to work in this manner for security. Because an RTD server can be installed on a computer without the user's knowledge, and because an RTD server requires no user interaction to function, Excel notifies users when an RTD server is present. They can then disable it if they want to.

NOTE: There are two cases in which an RTD server may ignore the security settings that are defined by the user:

• The RTD server has been digitally signed. Like digitally signed Microsoft Visual Basic for Applications (VBA) macros, a digitally signed RTD server can run even with High security set.
• The RTD server is running on a remote computer that is using DCOM. In this case, Excel depends on DCOM to handle security for the RTD server and assumes that it is safe to run the RTD server if DCOM allowed it to start.

For Office Excel 2007

In Excel 2007, RTD security is no longer tied to the macro security settings. Instead, RTD servers are governed by the Add-ins security settings. To examine or modify your add-in security settings, follow these steps:

1. Click the Microsoft Office Button, and then click Excel Options.
2. Click Trust Center and then click Trust Center Settings.
3. In the Trust Center dialog box, click Add-ins.

If the Disable all Application Add-ins check box is selected, no RTD servers can run. If the Disable all Application Add-ins check box is cleared, you may experience the following behavior:

• If the Require Application Add-ins to be signed by Trusted Publisher check box is cleared, any RTD server can run.
• If the Require Application Add-ins to be signed by Trusted Publisher check box is selected, the user is prompted to enable the RTD server if the publisher of the server has not already been added to the list of Trusted Publishers. If the RTD server is digitally signed, you can add the server to the Trusted Publishers list.
• If the Disable notification for unsigned add-ins check box is selected, you are not prompted to enable the RTD server unless it is digitally signed. Any unsigned RTD servers are not loaded.

For more information about RTD servers, click the following article numbers to view the articles in the Microsoft Knowledge Base: