How do I use 3rd party clamav signatures for spam & phishing

[ram]

I would like to use 3rd party signatures available with Clamav for spam
and phishing.   But I assume MailScanner would  marks mails caught by
these as Virus , rather than spam. 

What do you folks recommend on 
a) Using such signatures for clam for  large traffic servers 
b) Using clamav module for SA 
c) How do I avoid getting spams marked as virus 


Thanks
Ram