Stallings' Threats (Stallings, 1999) Source Normal S S sends D 1,000,000 Interception Modification Security Problems Typical Solution Destination Source Destination S sends D 1,000,000 S (C)onfidentiality Encryption Private key Public key H H knows it Destination Source S sends D 1,000,000 S D (I)ntegrity Check-Sum Hashing H S sends D 500 Interruption Source S S sends D 1,000,000 Source Fabrication S H Destination (A)vailability D receives nothing Destination Firewall Intrusion Prevision High Availability Business Continuity (A)uthenticity Strong Authentication Digital Certificate H S charge you 5000 Figure 6. Stalling's threats (Stallings, 1999)