Anti-virus on Citrix Servers

Based on Citrix Consulting experience, the antivirus software should be configured as follows:
• Scan on write events only
• Scan local drives only
• Exclude the pagefile from being scanned
• Exclude the Print Spooler directory to improve print performance
• Exclude the \Program Files\Citrix folder from being scanned (the heavily accessed local host cache and Resource Manager local database are contained inside this folder)

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Also worth reading is this blog post on the same topic.