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deny by default

Refuse everything, then allow only what's listed.

A deny-by-default policy rejects any traffic or action not explicitly allowed by a rule, ending a firewall rule list with deny all.

Examples

  • The router's firewall lets the IoT VLAN reach only the broker's port, then a final rule denies everything else.

  • A new device on the IoT VLAN can't reach the office network until someone writes a rule allowing it.

See also

network segmentation VLAN least privilege
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