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Sits between two networks Used to protect one from the other Places a bottleneck between the networks All communications must pass through the bottleneck – this gives us a single point of control. Compare network and transport protocols to a database of rules and
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Sits between two networks • Used to protect one from the other • Places a bottleneck between the networks • All communications must pass through the bottleneck – this gives us a single point of control
Compare network and transport protocols to a database of rules and then forward only the packets that meet the criteria of the rules. • Implemented in routers and sometimes in the TCP/IP stacks of workstation machines • in a router a filter prevents suspicious packets from reaching your network • in a TCP/IP stack it prevents that specific machine from responding to suspicious traffic • should only be used in addition to a filtered router not instead of a filtered router
Since an enterprise owns the computing and network facilities used by employees, it is perfectly within it’s rights to attempt to limit internet access to sites that could be somehow related to business • Since the proxy server is a natural bottle neck for observing all of the external requests being made from the internal network it is the natural place to check content • This is usually done by subscription to a vendor that specializes in categorizing websites into content types based on observation • Usually an agent is installed into the proxy server that compares URL requests to a database of URLs to reject • All access are then logged and reported, most companies then review the reported access violations and usually a committee reviews and decides whether or not any personnel action should be taken (letter of reprimand, dismissal, etc) • Sites that are usually filtered are those containing information about or pertaining to: • Gambling • Social Networking sites.
Used to connect two private networks via the internet • Provides an encrypted tunnel between the two private networks • Usually cheaper than a private leased line but should be studied on an individual basis • Once established and as long as the encryption remains secure the VPN is impervious to exploitation • For large organizations using VPNs to connect geographically diverse sites, always attempt to use the same ISP to get best performance.
Blocks packets based on: • Source IP Address or range of addresses. • Source IP Port • Destination IP Address or range of addresses. • Destination IP Port • Some allow higher layers up the OSI model. • Common ports 80 HTTP 443 HTTPS 20 & 21 FTP 23 Telnet 22 SSH 25 SMTP
http://www.bu.edu/ • http://www.comodo.com/resources • http://www.howstuffworks.com • http://www.wikipedia.org/ • http://technet.microsoft.com