Incoming message packets are intercepted and screened for {HEAD ~ readily discoverable characteristics} indicative of {TAIL ~ an infected message} 
indicative of
Incoming message packets are intercepted and screened for { HEAD ~ readily discoverable characteristics } indicative of { TAIL ~ an infected message }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL