Firewalls improve network security by:

1. _Controlling incoming and outgoing network traffic_: Firewalls act as a barrier between a trusted network and an untrusted network, such as the internet.

2. _Blocking unauthorized access_: Firewalls prevent hackers and malicious software from accessing the network.

3. _Hiding internal IP addresses_: Firewalls conceal internal IP addresses from external attackers.

4. _Preventing denial-of-service (DoS) attacks_: Firewalls can detect and prevent DoS attacks that aim to overload the network.

5. _Logging and alerting_: Firewalls provide logs and alerts for suspicious activity.

6. _Network segmentation_: Firewalls can segment the network into smaller, isolated segments.

7. _Stateful packet inspection_: Firewalls examine packets and ensure they meet security criteria.

8. _Virtual private network (VPN) support_: Firewalls can establish secure VPN connections.

By implementing a firewall, networks can significantly reduce the risk of security breaches and protect sensitive data. Firewalls are a crucial component of network security and are often used in conjunction with other security measures, such as intrusion detection systems and antivirus software.