Understanding and Establishing Important Firewall Rules for Small Business Security

As a small business owner, you’re a master of juggling tasks. Cybersecurity might feel like one more ball in the air, often relegated to the “later” pile. But consider this: if there’s one security measure that forms the bedrock of your digital protection, it’s your firewall. Neglecting its proper configuration is like leaving your front door unlocked. 

Fortunately, establishing strong firewall rules doesn’t have to be complicated. In this in-depth guide, we’ll break down what firewalls do, identify the essential rules every small business should implement, explain how to set them up effectively, and provide tips for long-term security. If you’re ready to take a crucial step towards a more secure future for your business, this is the guide for you.

Why Do Firewall Rules Matter?

With today’s hyper-connected environment, every device in your office (laptops, printers, etc.) is a potential doorway for cybercriminals. A 2023 Hiscox study found that 53% of SMBs experienced a cyberattack in the past year, with average damages exceeding $25,000 per incident. Why? Because too many of them lack proper cybersecurity protection, specifically properly configured firewalls.

A firewall is basically your company’s online security guard. It sits between your internal network and the outside world, monitoring and managing traffic over the internet based on a predetermined set of rules. Picture the bouncer at a nightclub checking what’s entering, what they have with them, and whether they can even get in at all.

When you forget to set up your firewall or permit rules too permissive, you’re leaving the front door wide open to ransomware, malware, and phishing. On the other hand, too restrictive rules will cut off access to essential tools your team needs to do their job. That’s why building the right firewall strategy is all about striking a thoughtful balance.

Key Concepts Small Businesses Need to Know About Firewall Rules

Before we dive into some rule proposal suggestions, there are a couple of basic concepts about firewalls that you might want to get familiar with first. These will make you less nervous and self-assured come change time. 

Inbound vs. Outbound Traffic

Inbound traffic is data that’s attempting to enter your network from outside, like when a customer submits a form on your site. Outbound traffic is data your internal network is passing through, like when employees send mail or use web-based services.

A good firewall keeps close tabs on both directions, letting in only safe, necessary traffic in or out.

Allow vs. Deny Rules

All firewall rules are to allow or deny traffic. The intent is to allow only what is important to your business and deny the rest.

• Allow Rules – These authorize specifically for certain types of safe traffic to pass through.
• Deny Rules – These block unwanted or harmful traffic based on various conditions like IP address, port, or protocol.

The default security attitude has to be: “If it’s not explicitly allowed, it should be blocked.”

Ports and Protocols

Certain ports and protocols are employed by network services to communicate. For example, web traffic typically operates on port 80 (HTTP) or port 443 (HTTPS). Knowing which ones your business relies on will help you create your rules block unnecessary ports while keeping necessary ones open.

Must-Have Firewall Rules for Common Network Services

Let’s talk about the critical firewall rules that most small businesses must include to protect their day-to-day activities without hampering workflow:

Web Browsing (HTTP/HTTPS)

Allow outgoing traffic on port 80 (HTTP) and port 443 (HTTPS) to allow employees to surf websites. To make it more effective, use DNS filtering tools to block access to websites on pages that are well-known for hosting malware or phishing scams.

Email Services (SMTP/IMAP/POP3)

Email is still the number one threat vector for malware. Allow only the specific outbound ports your email service uses: SMTP (port 25), IMAP (port 143), and POP3 (port 110). If you’re hosting your own email server, restrict inbound access with spam filtering and antivirus scanning.

Remote Access (RDP/VPN)

If you’ve got remote employees, you can use services like Remote Desktop Protocol (RDP) or VPNs. Allow these services to a limited set of IP addresses and use multi-factor authentication. Leaving remote access open is open-shutting-yourself-to-hackers. 

File Sharing (SMB/FTP)

Turn off FTP (port 21) and SMB (port 445) unless there is an utmost need for them. They are commonly used by ransomware and should be avoided or limited to usage within the network. Make use of safe alternatives like encrypted file-sharing networks.

How to Configure Basic Firewall Rules on Popular Devices

Now that you know which rules you need, let’s walk through how to actually set them up. While each brand has its own layout, most firewalls follow the same general steps.

Step 1. Log into the Firewall’s Admin Console

Start by opening a web browser and entering your firewall’s IP address (commonly something like 192.168.1.1 or 192.168.0.1).

You’ll be prompted to log in using administrator credentials. If you’re unsure of these details, refer to your device’s documentation or reach out to your IT provider for help.

Tip – Change default login credentials if you haven’t already, leaving them unchanged is a security risk.

Step 2. Find the Firewall or Security Settings

Once inside the admin console, look for a section labeled Firewall, Security, Access Control, or Advanced Settings.

This is where you’ll manage your traffic rules-adding, editing, or deleting them as needed.

Tip – Many devices have a built-in search bar or navigation menu-use it to jump straight to the firewall settings.

Step 3. Set Up a New Rule

Click “Add Rule” or “Create Rule.” You’ll be prompted to define the following:

• Direction – Choose whether the rule applies to inbound (incoming) or outbound (outgoing) traffic.
• Action – Decide whether to allow or block the specified traffic.
• Source and Destination IP Addresses – Define where the traffic is coming from and going to (can be a single IP, a range, or “any”).
• Port and Protocol – Specify which ports (e.g., 80 for HTTP, 443 for HTTPS) and which protocols (TCP, UDP, etc.) the rule applies to.
• Schedule (optional) – Some firewalls let you enable the rule only during certain times (useful for work hours or off-peak periods).

Tip – Be specific when setting IPs and ports to avoid unintentionally blocking important traffic.

Step 4. Save, Apply, and Test Your Settings

After saving your new rule, most firewalls will prompt you to apply the changes. Once that’s done:

• Test your network or application to confirm it’s working as expected.
• If something breaks (e.g., a service stops working), revisit the rule to ensure it’s not blocking essential traffic.
• Some firewalls offer a “log” or “monitor” section to see how rules are affecting traffic in real time.

Tip – If troubleshooting, try temporarily disabling the rule rather than deleting it. That way, you can easily re-enable it once you identify the issue.

Best Practices for Managing Firewall Rules

Firewall administration is a continuous effort that needs round-the-clock vigilance to make your network stay secure. It’s not setting rules and leaving them be one needs to keep monitoring and make adjustments to maintain robust security. Here are a few key practices to make sure your firewall runs smoothly and defends your systems:

Implement the Principle of Least Privilege

Only grant the minimum privilege necessary for a device or user to perform its task. Each open port or authorized protocol represents potential vulnerabilities, so boot unnecessary access. By adhering to the Principle of Least Privilege, you will be reducing your network attack surface, such that users or devices are capable of accessing just what they need and not anything else.

Maintain a Rule Log

Record every firewall rule that requested it, what it does, and when it was applied. Maintaining a log with lots of detail is a lifesaver when it’s time for troubleshooting or compliance audit seasons. This log provides visibility and allows you to ensure that, if things do go wrong, you have an easy record to help identify and fix the problem immediately.

Make Use of Rule Groups

Grouping similar firewall rules into sets simplifies handling and reduces the risk of misconfiguration. For instance, create distinct groups of “Remote Workers” and “Guest Devices” with independent access privileges. This approach simplifies making changes for specific groups without affecting others. It also ensures consistency and reduces the administrative burden of working with a large set of individual rules.

Regular Cleanup

Unused and old firewall rules are a security threat. Over time, they accumulate and even create holes. Set up a schedule (ideally once a quarter) to review and pare down your list of rules. Remove unused rules and consolidate duplicate rules. Regular housekeeping ensures a slimmed-down and safe firewall configuration, which saves on unnecessary complexity and vulnerabilities.

The Importance of Regular Firewall Rule Audits

Firewalls aren’t a “set-it-and-forget-it” solution. As your business evolves, so should your firewall rules. Employees come and go, new services are added, and older apps are retired. That’s why conducting regular firewall audits is essential.

Audits help you:

• Detect outdated, duplicated, or unnecessary rules
• Identify security gaps or overly permissive access
• Stay compliant with industry regulations

Most contemporary firewalls come equipped with logging and reporting functionality that simplifies the identification of trends or malicious activity. Utilize this information to actively make adjustments prior to vulnerabilities being exploited.

Final Thoughts and Next Steps

Spend time learning, installing, and configuring your firewall. This is one of the best cyberinvestments your business can possibly make. You don’t necessarily have to be an IT specialist to work from the defaults, but having some idea of what to do for you is an enormously empowering advantage.

Ready to Lock Down Your Firewall Like a Pro?

Our experts are here to assist small businesses in establishing solid, no-nonsense security foundations (without all the tech jargon).

Call us at (407) 389-3013 or contact us here to learn about intelligent firewall solutions that can fit your company. Your firewall doesn’t need to be covert. With the right rules installed, it’s your company’s first and best line of defense.