A firewall is a network securing hardware or software. Its main purpose is to check the inflow and outflow network traffic using an analysis of data packets and according to the set rules, it permits or rejects access to the computer. It bridges an internal network of the computer and an external source of network e.g. internet which is taken as insecure and cannot be trusted. For most of the private computers there is internal software that protects it from the external threats of the public internet. If you are interested in McAfee Internet Security, please don’t forget a McAfee promo code:
The firewall technology sprout in last years of the 1980’s, days in which the internet had just be introduced for connectivity around the globe. Initially there was the use of routers for internal network protection.
The first publication on the internet filter technology was done in 1988 by engineers of Digital Equipment Company and the publication was referred to as Packet filter. The filters operated by scrutinizing data transfers between computers online. If a data pocket corresponded to a rule in the filter, the data packet had to be discarded and a message was sent to the source indicated “error responses’’. A perfect example is if a filter is programmed to reject a network source such as telnet access the filter wall blocks it and its TCP protocol.
The second filter is called ‘stateful’ filters developed in 1989 in the AT&T Bell laboratories. They were mostly referred to as circuit level filters. These ones worked faster than the packet filters and they operated up to the transport layer (layer 4) in the OSI structured model. They operated in such a way that they retained data packets until enough information of the packet was gathered and the data packet is either allowed access or denied. Their main test criteria in its static rules are the ‘connection state’.
The third filter to be developed is the Application layer filter. It is highly advantageous in the fact that it has ability to detect an attempt by a non permitted protocol to bypass the filter on a certified port or also detect the harmful exploitation of a protocol.
Types of filter depend on the location at which communication is occurring. Types include:
Network layer also referred to as packet filters have a relatively low operating levels that do not allow packets unless they meet the established set of rule. The network layer filters are subdivided into two; stateful filters which maintain context for sessions (active) and use the maintained state to process packets and allow or deny access based on the source and the IP address , Stateless filters which require a less memory and are a bit faster especially when filtering simple data packets. Phishing Technique for Fishing the Humans by Hackers.
The application –layer filters monitor an application source by screening all data into and out of the application source. Once the packets are screened and inspected, the networked Worms and Trojans of the computer are prevented from spreading to other destinations. The application filters operate on the basis of whether a selected connection should be allowed on a given process.
A proxy provider can also act as a filter through responding to connection requests. It also operates from a selected network to a stated network application. Personal computers should be fitted with network filters to avoid hazardous attack from other networks