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The default CPU usage limit for McAfee On-Access scans is 30 percent. However, when McAfee scans a network drive the antivirus is forced to use a third-party driver that does not respect the 30 percent limitation.Therefore, if you permit McAfee to scan the network drives, McAfee will use all available CPU time to scan as much of the network as the computer has access to.
McAfee on the network servers already scans the network drives in real time. The network drives derive no additional benefit from being scanned by workstations.