The proliferation of mobile computing devices and local-area wireless networks has fostered a growing interest in location-aware systems and services. In this paper we present RADAR, a radio-frequency (RF) based system for locating and tracking users inside buildings. RADAR operates by recording and processing signal strength information at multiple base stations positioned to provide overlapping coverage in the area of interest. It employs techniques that combine empirical measurements with signal propagation modeling to enable location-aware services and applications. We present concrete experimental results that demonstrate the feasibility of using RADAR to estimate user location with a high degree of accuracy. 1

This paper describes an approach to monitoring events on a large number of servers and workstations. While modern UNIX systems are capable of logging a variety of information concerning the health and status of their hardware and operating system software, they are generally not configured to do so. Even when this information is logged, it is often hidden in places that are either not monitored regularly or are susceptible to deletion or modification by a successful intruder. Also, a system administrator must often monitor several, perhaps dozens, of systems. To address these problems, our approach begins with the modification of certain system programs to enhance their logging capabilities. In addition, our approach calls for the logging facilities on each of these systems to be configured in such a way as to send a copy of the critical system and security related information to a dependable, secure, central logging host system. As one might expect, this central log can see a megabyte...

International IP network traffic is evaluated for applications utilizing the TCP transport protocol. This evaluation is based on an analysis study performed in January 1992 across an infrastructural connection between Japan and the PACCOM network. This traffic measurement allows an examination of the current status of international information flow. Such analyses are a first, and essential, step toward a better understanding of the type, quantity, and breadth of international traffic flow. They can provide not only confirmation or refutation of intuitions and existing paradigms related to data exchanges, but also a fundamental framework upon which to base future network management, planning and design.

Increasingly large numbers of people communicate today via electronic means such as email or news forums. One of the basic properties of the current electronic communication means is the identification of the end-points. However, at times it is desirable or even critical to hide the identity and/or whereabouts of the end-points (e.g., human users) involved.

A classifier to determine page quality from an Optical Character Recognition (OCR) perspective is developed. It classifies a given page image as either "good" (i.e., high OCR accuracy is expected) or "bad" (i.e., low OCR accuracy expected). The classifier is based upon measuring the amount of white speckle, the amount of broken pieces, and the overall size information in the page. Two different sets of test data were used to evaluate the classifier: the Sample 2 dataset containing 439 pages and the Magazines dataset containing 200 pages. The classifier recognized 85% of the pages in the Sample 2 correctly. However, approximately 40% of the low quality pages were misclassified as "good." To solve this problem, the classifier was modified to reject pages containing tables or less than 200 connected components. The modified classifier rejected 41% of the pages, correctly recognized 86% of the remaining pages, and did not misclassify any low quality page as "good". Similarly, it recognized...

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Corporate network firewalls are well-understood and are becoming commonplace. These firewalls establish a security perimeter that aims to block (or heavily restrict) both incoming and outgoing network communication. We argue that these firewalls are neither effective nor appropriate for academic or corporate research environments needing to maintain information security while still supporting the free exchange of ideas. In this paper, we present the Stanford University Research Firewall (SURF), a network firewall design that is suitable for a research environment. While still protecting information and computing resources behind the firewall, this firewall is less restrictive of outward information flow than the traditional model; can be easily deployed; and can give internal users the illusion of unrestricted e-mail, anonymous FTP, and WWW connectivity to the greater Internet. Our experience demonstrates that an adequate firewall for a research environment can be constructed for minim...

This paper describes our experience in developing and maintaining multi-platform parallel / distributed scientific computing software. We gained this experience while developing the parallel computation environment for //ELLPACK

Today, large numbers of people exchange information using electronic means such as e-mail or news forums. These services make it easy to identify correspondents. However, under certain circumstances, it is desirable or even crucial to hide the identity and/or whereabouts of the persons involved. The design and implementation of a system allowing individuals to converse electronically while remaining anonymous to each other and to additional intervening parties are presented. A number of potential attacks tailored to undermine the anonymity provided are discussed, as well as ways of countering them. We also compare the efficiency of the different solutions proposed. The system is called Babel, as it is written: Therefore is the name of it called Bavel; because there the Lord did there confound the language of all the earth: and from thence did the Lord scatter them abroad upon the face of all the earth. --Genesis 11:9 Keywords: e-mail, mix, anonymity, traffic analysis IBM Contents 1...

Python is an interpreted, object-oriented language suitable for many purposes. It has a clear, intuitive syntax, powerful high-level data structures, and a flexible dynamic type system. Python can be used interactively, in stand-alone scripts, for large programs, or as an extension language for existing applications. The language runs on UNIX, Macintosh, and DOS machines. Source and documentation are available by anonymous ftp. Python is easily extensible through modules written in C or C++, and can also be embedded in applications as a library. Existing extensions provide access to most standard UNIX library functions and system calls (including processes management, socket and ioctl operations), as well as to large packages like X11/Motif. There are also a number of system-specific extensions, e.g. to interface to the Sun and SGI audio hardware. A large library of standard modules written in Python also exists. Compared to C, Python programs are much shorter, and consequently much fa...