A customer is seeing an increase in the number of malicious files coming in from undetectable sources in their network. These files include doc and .pdf file types. The customer believes that someone

A customer is seeing an increase in the number of malicious files coming in from undetectable sources in their network. These files include doc and .pdf file types. The customer believes that someone has clicked an email that might have contained a malicious file type. The customer already uses a firewall with User-ID enabled. Which feature must also be enabled to prevent these attacks?