What does "default-deny" firewall rule mean?

The "default-deny" firewall rule indicates that only specified connections are allowed through the firewall. This means that the firewall will block all traffic by default, permitting only what is explicitly defined as safe or acceptable. This approach enhances security by minimizing possible entry points that could be exploited by unauthorized users or malicious entities.

In contrast to allowing all traffic until specified otherwise, the default-deny policy requires an administrator to actively set rules for accepted connections. This ensures a more stringent control over network traffic and helps in preventing potential threats. This rule is a fundamental principle of network security, as it significantly reduces vulnerabilities by ensuring that only trusted connections are established.