What is a Firewall?
Firewall is either a hardware device or software application that shields your PC from malicious attackers by monitoring and regulating the data that comes in and goes out of your network. It acts as a 24/7 filter, examining the details of each data packet, looking for any signs of threats and preventing them from passing.
There are many different types of firewalls – the best one for you depends on your network needs and security requirements. For example, a basic home firewall can be a simple packet filtering software or your router’s built-in firewall, while an enterprise-grade firewall might combine multiple technologies like deep packet inspection and stateful inspection.
In order to block unwanted data from entering your computer, a firewall analyzes the data in packets and compares them against a database of predetermined filters/flags. For example, a packet can be checked for its source, destination, or port number. If the information is not safe, it will be discarded. Alternatively, it can be compared against a list of known threats (which might include spam, spyware, backdoor hacks and more).
More advanced firewalls use deeper analysis techniques to identify malicious information. For instance, next generation firewalls (NGFW) perform stateful inspection which looks at each incoming and outgoing data packet from a macro-level perspective rather than on an individual basis. This allows them to take into account how each new device and user typically interacts with your network – and then enforce rules accordingly. This method of detection also enables firewalls to better protect against novel or zero-day threats.