Library items tagged: firewalls

In the real world a firewall is a solid barrier between a precious asset on one side and a hazard on the other. For example, we hope that there is a firewall between the passengers in a car and the petrol tank. A network firewall performs exactly the same role, protecting an asset inside the firewall from a hazard on the outside. Firewalls are often used to protect an organisation from hazards on the Internet but they can, and probably should, also be used within an organisation to separate different departments, working areas or networks.
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Testing Before any system is introduced into the production environment, it must undergo a period of testing and evaluation. This is usually done in a test environment away from the production infrastructure.
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There are a number of issues that need to be considered before a new firewall is deployed or an existing one replaced on an organisation’s network. Requirements Analysis Defining a requirements specification will allow a successful evaluation of the various solutions available. There are many different elements involved in a firewall solution and the balance which needs to be achieved between these will differ significantly between organisations.
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Overview Cisco offers the PIX firewall solution, acquired from Network Translation in 1995, along with the original Centri firewall which ran on the Windows NT® operating system. The Cisco PIX, however, runs its own proprietary system called PIX OS, currently at version 7. The PIX is a packet filtering firewall with stateful inspection, and there are several DPI features in the newer versions which enhance the rules that can be created.
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SmoothWall and IPCop For some time, projects have been running to establish dedicated appliances based upon Linux, such as firewalls and web caches. These projects provide a pre-configured tool specific to one task which is easy to implement and configure.
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Why use UNIX/Linux? Firstly, unless a network administrator is familiar with the UNIX/Linux platform, then it is not recommended that a UNIX/Linux firewall is implemented. It will be easier to maintain a secure system if the administrator has skills in maintaining the underlying operating system. UNIX/Linux systems typically rely on a CLI more than a GUI, making navigating the system more difficult for the first time user.
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Good Practice All firewalls work on the premise of rules configured to implement the site security policy. Rules are so critical to the operation of the firewall that it is vital they are fully understood before a firewall implementation is deployed.
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Design The perimeter of an organisation’s LAN is the obvious place to locate its security protection. However, the perimeter has moved: no longer is there just one ingress to a LAN, but many points of access. Wireless networks, modems, secondary Internet connections and the migration of laptops between networks mean the boundary is constantly moving.
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Different Types of Firewall Firewalls operate in different ways, depending on the layer on which they are implemented. Circuit level firewall: data link layer Various names are used for this type of firewall. It is the type provided whenever NAT and PAT technology are used (see 3.7).
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Matthew Cook, Loughborough University Authors and Contributors This document was put together by Loughborough University to share knowledge, experience and current trends surrounding firewall implementation with the JANET community. This Technical Guide is complemented by the JANET Training programme which provides courses covering multiple facets of firewall implementation as part of their extensive portfolio.