Background antivirus scanning has been enabled

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine if background antivirus scanning is enabled:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\VirusScan

If the Exchange Server Analyzer finds the value for the BackgroundScanning entry is set to 1, a warning is displayed.

When the BackgroundScanning registry entry is present and set to 1, all messages are rescanned in the background every time the antivirus program's signature file is updated. This behavior substantially impacts performance whenever an antivirus signature file is updated, and is therefore not recommended by Microsoft.

When you use a Virus Scanning Application Programming Interface (VSAPI) 2.0-based antivirus program and a client tries to open a message, a comparison is made to make sure that the message body and attachment have been scanned by the current virus signature file. If the current signature pattern file was not used to scan the content, the corresponding message is submitted to the antivirus program before that message is available to the client.

If the installed antivirus program does not include a user interface that allows you to disable background scanning, you can use the procedure below to control this behavior by modifying the registry on the Exchange Server computer.

Important:
This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To correct this warning

Open a registry editor, such as Regedit.exe or Regedt32.exe.
Navigate to:

HKLM\System\CurrentControlSet\Services\MSExchangeIS\VirusScan
In the right-hand pane, double-click the BackgroundScanning value.
In the Value Data field, change the value to 0.
Close the registry editor, and restart the Microsoft Exchange Information Store service, and your antivirus software services for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=256986).
For more information on the different types of antivirus scanning programs used by Exchange, see the Knowledge Base article 328841, "Exchange and Antivirus software" (http://go.microsoft.com/fwlink/?LinkId=3052&kbid=328841).