What is a Firewall?
A firewall is either a hardware device or software application that helps protect networks from attackers. It acts like a 24/7 security guard that monitors and regulates data traffic that tries to get into or out of your system. The most common way that a firewall does this is by using packet filtering or through a proxy service. This process looks at incoming data in the form of packets, comparing them to filters that help identify malicious data. If a packet is deemed safe, it is allowed to pass. This prevents hackers from stealing or gaining access to your network, computer systems, or personal information.
Firewalls are important because they block a whole host of threats like viruses, malware, backdoor hacks, spyware, and spam. They also stop data theft, spoofed IP addresses, DoS (denial of service) attacks, and even hijacking attempts.
The first firewalls were developed in the 1980s at Digital Equipment Corp. by moguls Mogul, Reid, and Vixie who worked on packet-filtering technology. These early firewalls checked out external connections before they could reach computers inside a network. This prevented hackers from using infected computers to infect other devices within the same network segment.
More advanced firewalls are capable of more serious protection than the circuit-level gateway type because they can examine a packet in more detail. For example, stateful inspection technologies combine packet filtering with TCP handshake verification to ensure that all incoming data is safe. These can also keep contextual data about vetted connections to build up a threat database. However, these types of firewalls typically put a strain on computing resources and can slow down the transfer of legitimate packets of data.