Abstract—Reliability and quality of service from information systems has been threatened by cyber intrusions. To protect information systems from intrusions and thus assure reliability and quality of service, it is highly desirable to develop techniques that detect intrusions. Many intrusions manifest in anomalous changes in intensity of events occurring in information systems. In this study, we apply, test, and compare two EWMA techniques to detect anomalous changes in event intensity for intrusion detection: EWMA for autocorrelated data and EWMA for uncorrelated data. Different parameter settings and their effects on performance of these EWMA techniques are also investigated to provide guidelines for practical use of these techniques. Index Terms—Anomaly detection, computer audit data, exponentially weighted moving average (EWMA), information assurance,

In order to accomplish dependable onboard evolution, we develop a methodology which is called guarded software upgrading (GSU). The core of the methodology is a low-cost error containment and recovery protocol that escorts an upgraded software component through onboard validation and guarded operation, safeguarding mission functions. The message-driven confidence-driven (MDCD) nature of the protocol elim-inates the need for costly process coordination or atomic action, yet guaranteeing the system to reach a consistent global state upon the completion of the rollback or roll-forward actions carried out by individual processes during error recovery. Aimed at validating the effectiveness of the MDCD protocol with respect to its ability, in a real-istic, non-ideal execution environment, to enhance system reliability when a software component undergoes onboard upgrading, we conduct a stochastic activity network model based analysis. The results confirm the effectiveness of the protocol as origi-nally surmised. Moreover, the model-based analysis provides to us useful insights about the system behavior resulting from the use of the protocol under various conditions in its execution environment, facilitating effective utility of the protocol.

Message-driven confidence-driven (MDCD) error containment and recovery, a low-cost approach to mitigating the effect of software design faults in distributed embedded systems, is developed for onboard guarded software upgrading for deep-space missions. In this paper, we first describe and verify the MDCD algorithms in which we introduce the notion of "confidence-driven" to complement the "communication-induced" approach employed by a number of existing checkpointing protocols to achieve error containment and recovery efficiency. We then conduct a model-based analysis to show that the algorithms ensure low performance overhead. Finally, we discuss the advantages of the MDCD approach and its potential utility as a general-purpose, low-cost software fault tolerance technique for distributed embedded computing.

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA’s scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA’s institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types: • TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA’s counterpart of peerreviewed formal professional papers but has less stringent limitations on manuscript length and extent of graphic presentations. • TECHNICAL MEMORANDUM. Scientific and technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis.

developed a new generation of avionics building block modules for use by multiple deep space missions, including future missions to Europa, Mars, and a comet. The key developments of the X2000 Avionics are a high performance flight computer, solid-state mass data storage, high-speed system I/O, solid-state power distribution, and power regulation and conversion. These components enable a modular and scalable design approach that results in a wide variety of avionics system architectures to meet diverse mission requirements and environments. The X2000 Avionics have been developed for use in extreme radiation environments such as those at Jupiter. The use of commercial standard interfaces and buses throughout the X2000 Avionics allow system designers to add functionality and further customize spacecraft architectures. This paper will describe the system architecture, the avionics components, the key performance and reliability requirements, and the current development status of the X2000 Avionics.

To assure dependable onboard evolution, we have developed a methodology called guarded software upgrading (GSU). In this paper, we focus on a low-cost approach to error containment and recovery for GSU. To ensure low development cost, we exploit inherent system resource redundancies as the fault tolerance means. In order to mitigate the effect of residual software faults at low performance cost, we take a crucial step in devising error containment and recovery methods by introducing the "confidencedriven " notion. This notion complements the message-driven (or "communication-induced") approach employed by a number of existing checkpointing protocols for tolerating hardware faults. In particular, we discriminate between the individual software components with respect to our confidence in their reliability, and keep track of changes of our confidence (due to knowledge about potential process state contamination) in particular processes. This, in turn, enables the individual processes in the spaceborne distributed system to make decisions locally, at run-time, on whether to establish a checkpoint upon message passing and whether to roll back or roll forward during error recovery. The resulting message-driven confidence-driven approach enables cost-effective checkpointing and cascading-rollback free recovery.