A firewall is a network device that monitors packets going in and out of networks and blocks or allows them according to rules that have been set up to define what traffic is permissible and what traffic isn’t.
There are several types of firewalls that have developed over the years, becoming progressively more complex over time and taking more parameters into consideration when determining whether traffic should or should not be allowed to pass. The most modern are commonly known as next-generation firewalls (NGF) and incorporate many other technologies beyond packet filtering.
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Initially placed at the boundaries between trusted and untrusted networks, firewalls are now also deployed to protect internal segments of networks, such as data centers, from other segments of organizations’ networks.
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