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Network-based signature generation (NSG) has been proposed as a way to automatically and quickly generate accurate signatures for worms, especially polymorphic worms. In this paper, we propose a new NSG system—PolyTree, to defend against polymorphic worms. We observe that signatures from worms and their variants are relevant and a tree structure can properly reflect their familial resemblance. Hence, in contrast to an isolated view of generated signatures in previous approaches, PolyTree organizes signatures extracted from worm samples into a tree structure, called signature tree, based on the formally defined "more specific” relation of simplified regular expression signatures. PolyTree is composed of two components, signature tree generator and signature selector. The signature tree generator implements an incremental signature tree generation algorithm from worm sample clustering, up-to-date signature refinement to efficient tree construction. The incremental signature tree construction gives insight on how the worm variants evolve over time and allows signature refinement upon a new worm sample arrival. The signature selector chooses a set of signatures for worm detection from a benign traffic pool and the current signature tree constructed by the signature tree generator. Experiments show that PolyTree cannot only generate accurate signatures for polymorphic worms with noise, but these signatures are well organized in the signature tree to reflect the inherent relations of worms and their variants. [ABSTRACT FROM AUTHOR]

This paper describes a high-resolution, real-time, three-dimensional shape measurement system using the modified two-plus-one phase-shifting algorithm. The data acquisition speed is as high as 60 frames/s with an image resolution of 640×480 pixels per frame. Experiments demonstrated that the system was able to acquire the dynamic changing objects such as facial geometric shape changes when the subject is speaking, and the modified two-plus-one phase-shifting algorithm can further alleviate the error due to motion. Applications of this system include manufacturing, online inspection, medical imaging, compute vision, and computer graphics. [ABSTRACT FROM AUTHOR]

Nowadays the largest commercial database management systems are on the order of a terabyte. Emerging applications such as scientific databases for the Earth Observing System are expected to produce on the order of a terabyte of data per day. Applications requiring such data volumes also exist in the commercial arena, e.g., design databases. The objective is to achieve competitive efficiency in conjunction with a high-level query language interface, which provides efficiency of application implementation and maintenance. An issue of growing importance now is how to construct high performance, highly reliable systems out of a large number of components which individually have relatively small capacity and may be relatively unreliable. It is argued that the consensus problem is a basic building block in the construction of fault-tolerant systems. Applications of consensus algorithms to various problems in fault tolerant computing are given and the paper concludes with a vision of the role of the consensus problem in future systems design.

The author discusses the content of the December 1977 issue of the journal "ACM Computing Surveys." Data management systems store, update, and retrieve records. To help practitioners sort their way through the dozens of papers on record storage and accessing, Severance has classified record access methods on three axes: the frequency with which records are updated online, the proportion of records accessed on a particular retrieval, and the speed of response required by a user. For each combination of these three factors, he states which storage and accessing methods are the most practical and tells what you ought to read in order to use the recommended methods. His is a fresh approach to retrieving records about record-retrieving. Managers deal with large amounts of information. A management information system (MIS) is a computer-based data system that stores information of use to managers, and presents it as needed in the form of summaries, reports, and forecasts. Many programmers spend a good deal of time worrying whether they have implemented an efficient algorithm." Complexity theory" has been looking for years into such questions as: What is the fastest possible time in which a problem can be solved? What is the fastest known algorithm for solving it? If the fastest known algorithm has too much overhead, how well a given heuristic algorithm does.