Why Identical Firewall Rules Behave Differently Across AWS, Azure, Google Cloud and Oracle

Copying a firewall rule between cloud providers can unintentionally widen access, even when the port and intent appear identical. AWS security groups are stateful and allow-only, while Azure relies on priority-ordered rules with explicit denies and built-in defaults. Google Cloud applies an implied egress allow at the lowest priority, which can undermine a deny-everything policy if egress is not handled explicitly. Oracle security lists are stateless by default, so a rule copied from a stateful platform can break return traffic and tempt teams into overly broad fixes. The article warns that translating security group references into broad CIDR ranges and differing logging behaviours can silently expand exposure and hide evidence until an audit or incident.