Syntax errors on match_glob?

If you use reject, instead of TCP::release, the TCP connection will be reset.

 
 when HTTP_REQUEST {  
    if { [string tolower [HTTP::host]] contains "domain.com" }{  
        Reset the TCP connection 
       reject 
  
        End processing this rule event 
       return  
    }  
 }  
 

It might be more secure to positively define which host header values you do want to allow and send a reset for all others. You could do this for a single host as you've done above, or create a list of the allowed host header values in a datagroup (called a class in the bigip.conf).

Single allowed hostname:

 
 when HTTP_REQUEST {  
    if { not ([string tolower [HTTP::host]] contains "allowed.domain.com")}{  
        Reset the TCP connection 
       reject 
  
        End processing this rule event 
       return  
    }  
 }  
 

Multiple allowed hostnames defined in a datagroup called allowed_hostnames:

 
 when HTTP_REQUEST {  
    if { not ([matchclass [string tolower [HTTP::host]] contains $::allowed_hostnames])}{  
        Reset the TCP connection 
       reject 
  
        End processing this rule event 
       return  
    }  
 }  
 

Aaron