[ Glossary ]

Any-Any Rules

An any-any rule is a firewall or cloud security group rule that permits traffic without restricting the source, destination, or service, often written as "any/any/any" or "any/any/accept." It matches almost everything that reaches it, which means it can allow far more access than anyone intended, including paths an attacker could use to move through the network undetected.

What Is an Any-Any Rule?

Key takeaways

An any-any rule allows traffic from any source to any destination over any service, instead of naming the specific access a business need requires.
These rules usually start as temporary fixes, troubleshooting shortcuts, or leftover defaults, then stay in place because no one tracks ownership or revisits them.
They are a leading contributor to policy bloat and lateral movement risk, since they open broad lanes an attacker can use once inside the network.
Finding and narrowing any-any rules is a routine part of firewall rule cleanup, segmentation work, and continuous compliance.

Why Any-Any Rules Matter

An any-any rule looks simple on paper: one line, three fields set to "any." In practice, it's one of the riskiest patterns a firewall rule base can contain. Because it doesn't specify a source, destination, or service, it permits whatever traffic happens to match, far beyond what the person who wrote it was trying to solve for. A single any-any rule can quietly undo the intent of every other rule around it.

This matters because firewall rules are supposed to express a specific decision: this source, to this destination, over this service, for this reason. An any-any rule skips that decision entirely. It's the clearest example of why apparently simple rules can produce unintended results, and it's a pattern every firewall administrator eventually finds buried somewhere in a rule base they didn't build from scratch.

How Any-Any Rules Happen

Most any-any rules aren't malicious or even careless in the moment. They show up for reasons like:

Troubleshooting under pressure. An application isn't connecting, and a broad rule gets added to confirm it's not a firewall problem, then never gets narrowed or removed.
Migration and consolidation shortcuts. Teams merging acquired networks or moving to a new platform sometimes use a wide-open rule as a bridge, intending to tighten it later.
Default or legacy configurations. Older rule sets, inherited devices, or vendor defaults can include permissive catch-all entries that predate current ownership.
Unclear ownership. When no one is accountable for a rule's business purpose, it's easier to leave a broad rule in place than to investigate whether it can be safely narrowed.

A Realistic Example

A security team inherits a firewall from an acquired subsidiary. Buried near the bottom of the rule base is a rule allowing any source, any destination, and any service, with no comment and no clear owner. It was likely added years ago to get two systems talking during a deployment crunch and never revisited. The team doesn't know what depends on it, so it stays. Meanwhile, that rule sits active across every device inheriting the same policy template, quietly permitting far more access than any current business process requires.

The Operational Consequence

Any-any rules create risk in two directions. First, they expand the attack surface: if an attacker reaches a segment governed by an any-any rule, they can move laterally with little resistance, regardless of how well other parts of the network are segmented. Second, they create audit and compliance exposure. Frameworks and internal standards increasingly expect documented, least-privilege access, and an undocumented any-any rule is difficult to justify to an auditor or a security lead asking why it exists. Left alone, these rules also make every future change riskier, because no one fully understands what traffic they're carrying.

Key Components and Best Practices

Addressing any-any rules usually involves:

Usage analysis. Reviewing traffic logs to see what's actually flowing through the rule before deciding whether it's needed at all.
Ownership and business justification. Assigning a documented owner and reason for any rule broader than necessary, so decisions aren't made blind.
Narrowing, not just deleting. Replacing "any" with the specific sources, destinations, and services that traffic analysis shows are actually required.
Recertification. Periodically revisiting rules, including any that remain broad for a legitimate reason, so exceptions don't become permanent by default.

Common Challenges

The hardest part of fixing an any-any rule usually isn't technical, it's confidence. Teams often leave these rules in place because they're afraid narrowing or removing one will break something they can't see, especially in large, multi-vendor environments where rule relationships aren't well documented. Without traffic context and impact analysis, "clean up the any-any rules" becomes a project no one wants to own.

How This Connects to Network Security Policy Management and FireMon

Finding and remediating any-any rules is core to network security policy management (NSPM), the broader discipline of governing firewall rules, changes, and access over time. Policy is the control plane for network security, and an any-any rule is a sign that the control plane has gaps.

FireMon, the founder of NSPM, helps teams find any-any rules across multi-vendor firewalls and cloud security groups, see whether they're actually in use, and narrow or remove them through a documented review process rather than guesswork. That visibility supports reduced risk, stronger audit evidence, and a cleaner rule base without disrupting the connectivity the business depends on.

Frequently Asked Questions

Not always, but it's almost always worth scrutinizing. In rare cases, a temporary, well-documented any-any rule might support a specific, time-boxed need, but one left in place without an owner or a review date is a risk regardless of why it was created.

An any-any rule is overly broad in what it permits; a shadowed rule is one that never gets evaluated because an earlier, broader rule already matches the same traffic. An any-any rule can actually cause shadowing elsewhere in the rule base. For more on that pattern, see FireMon's resources on firewall rule management.

They typically lack a clear owner, a documented reason, or usage data showing what depends on them, so removing one feels riskier than leaving it alone. Without traffic analysis and accountability, teams default to inaction.

Yes. Cloud security groups and network security groups can be configured with open source, destination, or port ranges, creating the same risk pattern as an any-any firewall rule, just in a different platform's syntax.

Teams typically search rule bases directly or use a policy management platform that normalizes rules across vendors so "any/any/accept" patterns can be queried consistently, rather than checking each device by hand.