Terminology Index
Glossary
2953 terms
D32
Default Deny
A security principle of blocking everything by default and explicitly allowing only what is needed, applied to firewalls, access control, and network policy. It fails safe, since anything not expressly permitted is denied.
Default deny inverts the risky 'allow unless blocked' posture: the baseline is to refuse, and each permitted flow or access must be explicitly added. In networking it means firewall and policy rules permit only required traffic and drop the rest; in access control it means no access unless granted. This fail-safe stance dramatically shrinks what an attacker can reach and is a cornerstone of segmentation and least privilege.
Introduced in: Networking Foundations
Examples
- A firewall that drops all traffic except explicitly allowed flows.
- Network policies permitting only required service-to-service connections.
- Access defaulting to none until a permission is explicitly granted.
Related
Firewall Rulerelates_toMicrosegmentationrelates_toFirewallrelates_toLeast Privilegerelates_toNetwork Policies Productionrelates_toDMZrelates_toFirewall Rulerelates_toIngressrelates_toMicrosegmentation Principlesrelates_toNetwork ACLsrelates_toNetwork Firewallsrelates_toNetwork Policies (K8s)relates_toSecurity Groupsrelates_to
