The purpose of firewalls in network security is to act as a barrier between internal networks and external threats. They monitor and control incoming and outgoing network traffic based on predetermined security rules. Firewalls help protect systems from unauthorized access, malware, and other cyber threats by filtering traffic and blocking malicious activity. They can be hardware-based or software-based, often utilized in combination for enhanced security. By establishing a secure periphery, firewalls play a vital role in safeguarding sensitive data and maintaining the integrity of networked environments.