Basic security principles, principle of least privilege trust, trusted computing basics, reference monitors, inline reference monitors and access control, secure multi party computation, secure two party models. Mobile code security Digital Defense: Issues in Security, and Critical Infrastructure Protection: Threats of viruses, worms, malicious codes, etc. models of propagation and their epidemic spread, dos attacks, defenses against hacking. DDoS, design of scalable test beds for simulation of attacks against critical infrastructures, architectures for robust and flexible Internet, ubiquitous, dependable and indestructible storage.