What is a Firewall?
Firewalls are the security guards that check the credentials of everything that moves into or out of your devices (computers, tablets, home networks) and determine whether it should pass or get blocked. They’re critical for preventing malicious and unwanted data from entering or leaving your network.
Firewalls inspect data packets on a per-connection basis to detect and block threats, such as malware and ransomware. They can be a hardware or software tool. Most off-the-shelf firewall solutions come preconfigured with a set of rules to help save time during deployment, as well as to ensure adherence to industry best practices and standard security configurations.
First-generation firewalls started with a simple packet filtering approach that examined each individual data packet and made decisions to allow or deny on the basis of predefined rules. They offered limited protection, however, as attackers were able to use sophisticated techniques like IP fragmentation to circumvent them. Second-generation firewalls, introduced in the early 2000s, added stateful inspection to improve security by tracking the state of active connections and evaluating traffic in context. However, they took a significant toll on network performance because they performed detailed analyses on every packet in each session.
Third-generation firewalls, introduced in the mid-2000s, offer a hybrid solution that integrates traditional firewall capabilities with advanced threat defense technologies. They include application-level gateways, which act as intermediaries between internal and external systems and intercept, evaluate, and filter traffic at layer 7 of the OSI model (the closest to end-user applications) to prevent attacks such as cross-site scripting and SQL injection.