tag:blogger.com,1999:blog-7968135.post-1092711528198154192004-08-16T19:58:00.000-07:002004-08-16T19:58:48.196-07:00Computer and network security needs have changed drastically over the past several years, and firewall technology has evolved to meet those new, more demanding needs. The traditional firewall was a fairly simple construct: It sat between the LAN (or in the case of personal firewalls, an individual computer) and the outside world of the Internet, and filtered packets coming in and in some cases, going out, based on information in the Layer 3 and 4 headers (IP, TCP, UDP, ICMP). The decision to accept or reject a packet was usually based on the source or destination address or port number. <br />A Firewall is a security measure that prevents unauthorized users from gaining access to a computer network or that monitors transmission of information to and from the network. Firewalls are essential in slowing down the transmission of viruses and worms, but can also be used to help decrease the amount of unwanted spam that the network’s clients receive. <br />As attackers grew more sophisticated and began to exploit higher layer protocols (DNS, SMTP, POP3, etc.), firewalls had to do more. Most business-class firewalls today perform at least some application layer filtering. Firewall is necessary to prevent application layer attacks and to filter for spam and viruses, or to perform content filtering to block objectionable Web sites based on content rather than just IP address. <br />Firewalls today are often more than one entry at the network gate. Vendors have added other features that aren’t strictly firewall functions. Almost all modern firewalls other than those at the very low end support VPN, and many either include caching to accelerate Web performance or offer add-on modules for that purpose. In fact, many vendors have started calling their products multifunction security devices or software, instead of simply firewalls. <br />firewall softwarehttp://www.blogger.com/profile/11056230181044279673noreply@blogger.com