Why VS API

Why Microsoft Exchange's Virus-Scanning Application Program Interface (VS API)?


Advantage of Trend Micro ScanMail for Exchange 2000
Microsoft strongly encourages the development and adoption of Exchange VS API-based antivirus solutions

  • ScanMail for Exchange 2000 running on the Microsoft Exchange VS API 2.0 is secure and preserves the integrity of the Information Store and its databases
  • The Microsoft Exchange product group is committed to providing enhancements to this API, bug fixes, documentation, and technical assistance to ISVs (as appropriate)
  • Antivirus solutions using Extensible Storage Engine API or any other undocumented API may corrupt the Information Store and its databases
  • The Microsoft Exchange product group does not provide any code updates, documentation, or technical assistance to address issues related to the use of a non-VS API-based solution
  • For Exchange customers using a non-VS API-based solution, Microsoft Product Support Services may ask the customer to uninstall/disable the antivirus solution to help identify issues, this may delay in final resolution
  • VS API enhances the current core feature set by providing abilities to optimize and configure the scanning process at multiple levels, as well as providing Exchange administrators with built-in functionality to monitor the performance of the new API
 

Trend Micro ScanMail for Exchange 2000 runs on the Microsoft Exchange virus-scanning API 2.0, which makes ScanMail for Exchange more secure since it does not make any changes to the attachment table. As a result, both protocols and access are through the information store database and all email attachments go through the Exchange virus-scanning API. This preserves the integrity of the Information Store and its database. In addition, the Microsoft Exchange product group is committed to providing enhancements to this API, bug fixes, documentation, and technical assistance to ISVs (as appropriate).

Antivirus products using the Extensible Storage Engine API (ESE API) or any other undocumented API, make changes to attachments and attachment tables to scan for viruses. This can potentially corrupt the Information Store and its database or destroy the attachment if data is not correctly managed. In addition, the Microsoft Exchange product group does not provide any code updates, documentation, or technical assistance to address issues related to the use of a non-VS API-based solution.

Running on the Exchange VS API, ScanMail for Exchange preserves single instance scanning on storage across the enterprise. Single-instance storage is usually used on a single Exchange server to save space so that only one copy of an attachment is stored if it has been sent to a group. ScanMail for Microsoft Exchange uses single-instance scanning of attachments as they are sent between different servers as well. Each server has a different Information Store and stores a copy of the attachment. However, ScanMail only needs to scan the attachment on one server and then it is flagged. When the copy is sent to another server, ScanMail on the new server knows that it has been scanned and does not scan it again.

ScanMail for Exchange running on Exchange VS API guarantees that all file attachments will be scanned before they are opened by the end-user.

Microsoft's Position on Antivirus Solutions for Exchange 2000

Microsoft recommends that customers deploy an antivirus solution based on the Exchange virus-scanning API 2.0. The VS API 2.0 is included in Microsoft Exchange, Service Pack 1 only. The Exchange product group is committed to providing enhancements to this API, bug fixes, documentation, and technical assistance to ISVs (as appropriate). An updated VS API is now available with Exchange 2000 SP1, which was released in June 2001. The new API enhances the current core feature set by providing the abilities to optimize and configure the scanning process at multiple levels, as well as providing Exchange administrators with built-in functionality to monitor the performance of the new API.

Microsoft also recognizes that other antivirus solutions for Exchange 5.5 and Exchange 2000 are available that do not use the VS API. The Exchange product group does not provide any code updates, documentation, or technical assistance to address issues related to the use of a non-VS API-based solution. For Exchange customers using a non-VS API-based solution, Microsoft Product Support Services may ask the customer to uninstall/disable the antivirus solution to help identify issues. Customers are free to reinstall/enable the software after the root cause of the issue is properly diagnosed. Microsoft may find it necessary to engage the ISV’s support organization to determine the root cause of the issue, which may delay the final resolution.

Microsoft strongly encourages the development and adoption of Exchange VS API-based antivirus solutions.

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