What are Firewall Rules?
When it comes to online security, firewalls are an essential tool for protecting data and networks from malicious cyberattacks. A firewall is a system designed to control access between networks, computers, and other systems. Firewall rules are an important part of this security system, as they determine which network traffic will be allowed to pass through the firewall and which traffic will be blocked. By having a clear set of firewall rules, businesses can protect their systems from potential threats while allowing legitimate users to access the services they need.
What are Firewall Rules?
The firewall rules are the access control mechanisms used by firewalls to safeguard your network from harmful applications and unauthorized access. They determine which types of traffic your firewall accepts and which are denied. A collection of firewall rules makes up the firewall access policy. They examine the control information in each network packet and block or allow them based on the criteria you establish. First, each package is evaluated from top to bottom, and its components are compared to policy rules components. The configured action of the first rule that matches the packet is then executed, together with all the steps provided in the rule’s defined parameters.
Why are Firewall Rules important?
Firewall rules are a critical network security component. These rules act as a filter between a company’s internal private network and external sources, allowing administrators to control traffic flow. By defining a set of conditions for traffic evaluation, firewall rules play an instrumental role in defending against cyber threats, unauthorized access, and safeguarding sensitive data.
The significance of firewall rules extends beyond mere access control. They also enforce a company’s security policies at the network level. Consistently updated and managed firewall rules ensure that firewalls only facilitate legitimate, secure traffic. Understanding firewall rules and their importance preserves the integrity of an organization’s data infrastructure.
How do Firewall Rules work?
A firewall evaluates each incoming and outgoing data packet against the firewall rules. If the packet matches one of the rules, the firewall allows the packet to pass through to its destination. Otherwise, it rejects and (if programmed to) reports it.
Firewall rules are configured as access control lists (ACLs), which are ordered lists of permissions defining traffic allowed or denied. A typical ACL includes an action (allow, deny, or reject) followed by conditions or parameters traffic must meet before the action is applied.
To ensure security, firewalls often use a “deny by default” policy, meaning that any traffic that doesn’t explicitly meet the criteria laid out in the firewall rules will be denied.
For a very simple example, you might have a rule that says, “Allow any traffic from IP address X to port Y.” When a packet arrives at the firewall, the firewall reads its source and destination. If the packet’s source is X and its destination is Y, it passes through. If, on the other hand, its source is Z—or if its source is unidentified – and the destination is Y, it is denied.
How is it established?
A firewall rule may be based on several factors, including:
- IP addresses. The rule may specify source and/or destination IP addresses. For example, a rule might allow traffic from a certain range of IP addresses while blocking all others.
- Ports. The rule could allow or deny traffic depending on the network ports and protocols (TCP, UDP, ICMP, etc.). For instance, if a server is only intended to serve web traffic, it might only allow traffic on TCP ports 80 (HTTP) and 443 (HTTPS) while blocking all other ports.
- Direction. Firewalls can control inbound (incoming) and outbound (outgoing) network traffic. Rules can be set to control both directions.
- Content. Advanced firewalls can inspect the content of network traffic and allow or deny traffic based on this. For example, a rule could block traffic that contains malicious content.
Types of Firewall Rules
- Access Control Rules – Access control rules are crucial in defining which traffic the firewall permits to enter or exit a network. They are based on criteria such as IP addresses, port numbers, and protocols to make real-time decisions, enabling secure and controlled connectivity between different network zones.
- Network Address Translation Rules – Network address translation (NAT) rules are essential for routing traffic between private and public IP addresses. They translate addresses and ports of transiting packets, helping to obscure the internal network structure.
- Application-Level Gateways – Application-level gateways, or proxy firewalls, scrutinize traffic at the application layer. They apply security measures for specific applications. This allows for a more granular traffic inspection, ensuring the firewall allows only safe application traffic through.
- Stateful Inspection Rules – Stateful inspection rules monitor the state of active connections and make decisions based on the context of traffic. This method tracks each connection traversing the firewall and ensures only packets matching a known active connection can pass.
- Circuit-Level Gateways – Circuit-level gateways enforce security measures at the session layer of the OSI model. They monitor TCP handshakes across the firewall to ensure sessions initiate in a trusted manner, permitting or denying traffic without inspecting the packets deeply.
What are Inbound and Outbound Firewall Rules?
In a firewall ruleset, inbound rules identify the types of traffic the firewall allows in the network.
Inbound traffic rules detail allowed connections, originating ports, and source addresses. When there are no inbound rules specified, the firewall does not allow inbound traffic. Inbound rules protect the network from unsanctioned access, harmful entities, and DoS attacks.
Outbound rules determine the nature of traffic exiting the network, specifying permissible destination addresses, ports, and protocols. Without explicit outbound rules, the firewall blocks all outbound traffic by default.
Conclusion
Before configuring specific rules for your business’s firewall, make sure you study the network and know all your applications well. Which ones need to be protected? Which websites do your employees most frequently access? Are there any internet sources that they should never be able to access? Additionally, how extensive do your team’s allowlists and blocklists need to be?
Firewall rules should be configured intentionally by professionals who know the networking needs of the business. Be wise with your firewall configurations, instead of just creating rules willy-nilly — each should have a specific purpose that you can clearly explain. The more firewall rules are managed, the better they’ll be able to serve your IT department and the entire business.