Chapter 15 Unified Threat Management for FortiOS 5.0 : AntiVirus : Grayware scanning
  
Grayware scanning
Grayware programs are unsolicited software programs installed on computers, often without the user’s consent or knowledge. Grayware programs are generally considered an annoyance, but they can also cause system performance problems or be used for malicious purposes.
To allow the FortiGate unit to scan for known grayware programs, you must enable both antivirus scanning and grayware detection.
Enter the following command to enable grayware detection:
config antivirus settings
set grayware enable
end
With grayware detection enabled, the FortiGate unit will scan for grayware any time it checks for viruses.