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Linux Server Security, Second Edition
book

Linux Server Security, Second Edition

by Michael D. Bauer
January 2005
Intermediate to advanced content levelIntermediate to advanced
544 pages
23h 44m
English
O'Reilly Media, Inc.
Content preview from Linux Server Security, Second Edition
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
Principles of Intrusion Detection Systems
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451
Principles of Intrusion Detection Systems
In practical terms, there are two main categories of IDS: host-based and network-
based. A host-based IDS, obviously enough, resides on and protects a single host. In
contrast, a network-based IDS resides on one or more hosts (any of which may be a
dedicated “network probe”) and protects all the hosts connected to its network.
Host-Based IDSes: Integrity Checkers
Dedicated host-based IDSes tend overwhelmingly to rely on integrity checking. In
theory, host-based IDSes should use a much broader category of tools. Commercial
IDS products, such as ISS RealSecure and Marcus Ranum’s Network Flight
Recorder, both of which I categorize as Network IDSes, can use sophisticated meth-
ods (such as traffic analysis) on a single host, if desired.
Integrity checking involves the creation and maintenance of a protected database of
checksums, cryptographic hashes, and other attributes of a host’s critical system files
(and anything else you don’t expect to change on that system). The integrity checker
periodically checks those files against the database: if a file has changed, an error or
alert is logged. Ideally this database should be stored on a read-only volume, or off
the system altogether, to prevent its being ...
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Publisher Resources

ISBN: 0596006705Supplemental ContentCatalog PageErrata