User guide

164
McAfee
®
GroupShield
™
7.0 User Guide Settings & Diagnostics
On-access settings
11
2 In General, choose Allow Through or Remove depending on whether you want to allow
the email message through or delete it, if scanning fails.
3 In Microsoft Virus Scanning API (VSAPI):
 Select or deselect Enabled to specify whether VSAPI should be enabled or not.
 Select or deselect Proactive Scanning to specify whether or not to scan email
messages and files when they are written to the store.
 Select or deselect Background Scanning to specify whether background scanning
should be enabled or not.
You can use
Enable At and Disable At to schedule the background scanning.
 Type Scan Timeout (seconds) to specify a time to wait for a scan to wait before it
gets timed out.
 Check the Default option to use the default Number of Scan Threads, else deselect
the option and enter a desired value. We recommend you to use the
Default
option.
4 In
Transport Scan Settings:
Note
VSAPI is implemented at a very low-level in the Exchange Information Store. This allows
a virus scanning application to run with high performance, and guarantees that the
message will be scanned before any client can access the message or its attachment.
This allows messages and attachments to be scanned once before delivery, rather than
multiple times (depending on the number of mailboxes to which the message is
delivered). This single-instance scanning also helps prevent messages from being
re-scanned when a message is copied, which results in improved system performance.
Note
Proactive scanning is a type of scanning that is made possible by Microsoft
®
VSAPI. It
enables objects from the store to be scanned in order of priority.
Items passing in and out of the store receive a priority rating and are placed in a scanning
queue. The scanning queue allows prioritization and re-prioritization of items in the
queue.
For example, if a user tries to open an item that has not been scanned, it is assigned a
high priority, whereas items being saved or posted to public folders are assigned a low
priority. This is known as priority based queuing.
When all the high priority items have been scanned, scanning of lower priority items
begins. The latter scans on a first-in-first-out (FIFO) basis.
Note
Background scanning is a type of on-access scanning made possible within Microsoft
®
Exchange 2003/2007 by Microsoft
®
VSAPI, which does not scan all files on access,
reducing the scanner's workload. It scans the databases on which it has been enabled.
Background scanning is off by default.