Getting started; why security?; picking a security policy; strategies for a secure network; the ethics of computer security; warning; an overview of TCP/IP; the different layers; routers and routing protocols; the domain name system; standard services; RPC-based protocols; file transfer protocols; the r commands; information services; the X11 system; patterns of trust; building your own firewall; firewall gateways; firewall philosophy; situating firewalls; packet-filtering gateways; applicatio-level gateways; circuit-level gateways; supporting inbound services; tunnels good and bad; joint ventures; what firewalls can’t do; how to build and application-level gateway; policy; hardware configuration options; initial installation; gateway tools; installing services; protecting the protectors; gateway administration; safety analysis-why our setup is secure and fail-safe; performance; the TIS firewall toolkit; evaluating firewalls; living without a firewalls; authentication; user authentication; host-to-host authentication; gateway tools; proxylib; syslog; watching the network: tcpdump and friends; adding logging to standard daemons; traps, lures, and honey pots; what to log; dummy accounts; tracing the connection; the hacker’s workbench; introduction; discovery; probing hosts; connection tools; routing games; network monitors; metastasis; tiger teams; further reading;; a look back; classes of attacks; stealing passwords; social engineering; bugs and backdoors; authentication failures; information leakage; denial-of-service; an evening with berferd; the day after; the jail; tracing berferd; berferd comes home; where the wild things are: a look at the logs; a year of hacking; proxy use; attack sources; noise on the line; odds and ends; legal considerations; computer crime statutes; log files as evidence; is monitoring legal?; tort liability considerations; secure communications over insecure networks; an introduction to cryptography; the kerberos authentication system; link-level encryption; network-and transport-level encryption; application-level encryption; where do we go from here?; useful free stuff; building firewalls; network management and monitoring tools; auditing packages; cryptographic software; information sources; TCP and UDP ports; fixed ports; mbone usage; recommendations to vendors; everyone; hosts; routers; protocols; firewalls; bibliography; index.