1. Design a file access system to allow certain users read and write access to a file depending on authorization set up by the system. The instructions should be of the format READ(F, User A): Attempt by User A to read file FWRITE(F, User A): attempt by User A to store a possibly modified copy of F. Each file has a header record, which contains authorization privileges that is a list of users who can read and write.
2. A decentralized NIDS is operating with two nodes in the network monitoring anomalous inflows of traffic. In addition, a central node is present, to generate an alarm signal upon receiving input signals from two distributed nodes. The signatures of traffic inflow into the two IDS nodes follow one of four patterns: P1, P2, P3, P4. The threat levels are classified by the central node based upon the observed traffic by the two NIDS at a given time and are given by the following table If, at a given time instance, at least one distributed node generates an alarm signal P3, what is the probability that the observed traffic in the network will be classified at threat level ‘Medium'?