PC DoorGuard 3. A very extensive and thorough intrusion scanner that scans any media onyour PC for backdoors and trojan horses. PDG easily removes any found trojan with a click of abutton, together with any elements it may have left in registry/system files/memory. PDG alsoconstantly monitors your system to prevent further infection, using weekly updated trojan databaseconsisting of more than 5000 entries.