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The Do’s and Don’ts of a Firewall

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Having learned about the various kinds of the firewall, we must understand the various do's and don’ts of a firewall. This is not an exhaustive checklist. However, this is more from a guideline perspective as different environments demand a different set of strategies. The default action of any firewall should be to implicitly deny any packets not explicitly allowed. This means that if no rule states that the packet can be accepted, that packet should be denied, no questions asked - Default DENY. If you are not on the guest list, you can’t meet the president. Any packet entering the network that has a source address of an internal host should be denied. If you receive a letter from an outsider, how can the FROM address be your own address? There is no reason a packet coming from the Internet should have an internal source network address, so the firewall should deny it. No traffic should be allowed to leave a network that does not have an internal source address. If t

It’s the Middleman – Proxy Firewall

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How many of you have applied proxy for one of your friends during the attendance call in the class? If I assume, it’s a yes from everyone, you will have no difficulty in understanding this one. Proxy is someone who is acting on your behalf and acting as the middleman. We take a more detailed example in some time to clearly understand this. A proxy firewall stands between a trusted and untrusted network and makes the connection, each way, on behalf of the source. When you as a user, will send a request to, say connect, www.facebook.com, the request will go through the proxy firewall to check what request has been made. The proxy firewall will stop your connection, initiate a new connection on your behalf and wait for the incoming traffic. Surely, it finds that you have requested for a website which is quite known for leaking personal data, it stops the traffic and sends you a message that this website cannot be connected to. This is unlike the packet filtering firewall. Where

Which State are you in? I’m Stateful.

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In continuation with our series on understanding the firewalls, the next type is the stateful firewall. This one remembers and keeps track of what packets went where until each particular connection is closed. To understand this one, we need to take an example. If you watch a little bit of crime drama, you will find that in most cases the neighbor knows everything. He is spying day and night on you and others in the neighborhood. He knows that the man on the left side of the road deals in weed and goes out of the house in the night, the construction guy who takes long breaks inside the garage, the milkman who smiles and pours extra milk looking at the handsome guy that lives next door and so on. Most of the well-known protocols have a sequence of connecting. For eg – If you consider the TCP protocol which is a connection-oriented protocol, it goes through three steps before a connection is established. This is commonly known as the 3-way handshake. If my system wants to c

This One is all about Packets

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In the earlier blog post on the basics of the firewall, we learned what exactly is a firewall and what does it do? It’s time to learn about the various types of firewalls and how do they function. I will dedicate one post each to the types of the firewall, thereafter jumping to the various kinds of firewall architecture. Packet Filtering Firewall The packet filtering firewall is the most basic of all the firewall types. Taking a cue from the earlier discussed analogy of postman , this type filters the information packets based on rudimentary parameters such as source and destination address, port numbers, traffic direction. A postman also looks at your letter and filters or segregates them on the basis of pin codes, destination address, etc. Packet filtering is a firewall technology that makes access decisions based upon network-level protocol header values. The device that is carrying out packet filtering processes is configured with ACLs, which dictate the type of

The Curious Case of Firewalls

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If you are hearing about the term firewall for the first time, and consider it as a wall on fire, you are at the right place. Because that is the overall idea behind this!!! Firewall is one of the most used terms in the field of information security. A lot of people think that deploying this wall of fire will solve all of their problems. Is that so? What is it that a firewall does? Does it come in all shapes and forms? What is actually a firewall? Can I use a virtual firewall?  And many more… All your queries will be solved in this multi-part series on the firewalls. A firewall is used to restrict access to one network from another network. You can think of it as a fence which you implement to keep those pestering pedestrians at bay. The firewall can also help you segregate one network within the overall network from another network. It’s like a door which helps to separate various rooms. For example, if the security administrator wants to make sure employees cannot access

Crime Prevention through Environmental Design (CPTED) Approach

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Security design and access control are more than bars on windows, a security guard booth, a camera, or a wall. Crime prevention involves the systematic integration of design, technology, and operation for the protection of three critical assets-people, information, and property. Protection of these assets is a concern and should be considered throughout the design and construction process. The most efficient, least expensive way to provide security is during the design process. Designers who are called on to address security and crime concerns must be able to determine security requirements, must know security technology, and must understand the architectural implications of security needs. Consider the following picture of an office campus below. What do you observe? Note down what all do you think represents this campus. Here are some important points worth mentioning : Well-Paved footpaths. Proper guidance of people entering and leaving by giving them a design