- An international standard for the exchange of debit and credit transactions, such as bank debts, commercial invoices and purchase orders.
fīr´wâl) (n.) A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
There are several types of firewall techniques:
· Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
· Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.
In practice, many firewalls use two or more of these techniques in concert.