A Beginner’s Guide to Firewall Log Analysis for Small Businesses

Sanjay Seth, P J Networks Pvt Ltd

It’s barely making it past my third coffee — and I’ll still be buzzing from DefCon’s hardware hacking village. There’s nothing quite like a gaggle of hackers armed with screwdrivers and soldering irons to remind you of just how far network security has advanced, and how far people will attempt to stretch the envelope. But hey, that’s just cybersecurity life, eh? Things keep changing, and if you are an admin or a small business owner and you feel lost with your firewall logs Sysadmin blues, trust me, been there since early 2000s.

I began my career back in 1993 (yes, dinosaurs walked the earth back then) as a network admin managing voice and data multiplexers over PSTN. You want to hear about legacy, I fought the Slammer worm firsthand—before malware had smart, it was dumb chaos. And now as the owner of P J Networks Pvt Ltd, I help SMBs and banks (I recently completed three zero-trust upgrades) tame the otherwise wild beast of network security.

So, pull up a chair. Here’s a simple, to-the-point guide to using firewall log analysis as your secret weapon for network security for your small business.

Why Firewall Logs Are Critical for Security?

To set the stage: your firewall logs are the black box recorder of your network. They monitor not only what’s on the approved list to be let in, but what’s attempting to crawl through the gates. Like a surveillance camera in your digital “home.”

Small business owners typically overlook the functionality of logs. I know—logs tend to make no sense to most people. But here’s the thing…

• Firewall logs provide you with insights into traffic patterns.
• They notify you of intrusions that are blocked before damage is done.
• Logs help you identify misconfigurations or rogue users.
• They offer forensic data post-incident to assist in clean-up.

I remember a client — a small bank — paying no attention to the logs until a virus came out of nowhere and jumped inside to encrypt their systems. The analysis of the logs, after the fact, was almost like looking at a game replay: suspicious traffic hitting their network for weeks, no one seemed to be alarmed. Don’t let your business be the exception.

Specifically Actionable Trends to Watch in Your Firewall Logs

Logs can be like drinking from a firehose. The trick is knowing what to look for. Here’s a quick-hit list from decades in the business — and yes, a few hair-pulling moments.

Watch for:

• Multiple failed connection attempts — This may be bots doing brute-force logins or scan tools.
• Port activity that is out of the ordinary — Simply, traffic on ports that you never use. (Why is your firewall even open FTP ports these days?)
• Connections to odd IPs outbound — Malware usually phones home.
• Unexpected location login attempts — Especially for VPN or remote access
• Unusual data movement during the night — May indicate data exfiltration.
• Changes in the firewall rule sets — Auditors love this, so should you.
• Non-standard Protocols — Such as SSH on a non-standard port or unknown protocols.

PS: Not every denied packet is “evil.” Apps change sometimes, and your firewall can be a little confused. But it’s the patterns that count. One-off oddities? Usually nothing. Repeated, consistent hits? Get worried.

Configuring Alerts: Your Early Warning System

As a small business, you likely have not invested in a full-time security operations center (SOC). That’s fine. But you need alerts configured so you’re not face-planted in logs 24/7 (life’s too short).

What to alert on?

• Multiple brute-force attacks from same IP
• No approved changes to firewall rules
• Many packets from the same source are dropped
• Abnormal outbound traffic bursts.

Here’s what I suggest for SMBs:

• Keep alerts actionable. 100 alerts a day? No one will read them.
• Use triggers based on thresholds — e.g., 5 failed attempts in 10 minutes
• Even better: Bring alerts into email or messaging apps you actually open
• Don’t be shy about tuning or silencing noisy alerts — they lead to introduced false alarms.

And be honest with yourself; there is no substitute to looking at logs yourself every now and then. Automation helps. However, hackers change, your firewall does not catch everything.

Simple Techniques to Analyze Your Firewall Logs

Alright, let’s get hands-on. If you’re a small business diving into this for the first time, here’s how I would go about log analysis:

1. Know the Format of Your Firewall Logs
   Every firewall vendor has its own way of implementing logs. But you’ll usually see: timestamp, source IP, destination IP, port, action (allow/block), protocol, and sometimes user info.
2. Segment by Action
   Differentiate between allowed and denied traffic. Inverted lists: you now focus on denied but don’t neglect allowed—some allowed connections are suspicious as well.
3. Look for Patterns Over Time
   The daily lumbering through logs to monitor activity is monotonous (I picked that up quickly). Rather, choose an interval (daily or weekly), and look for patterns on IPs or ports.
4. Correlate with Business Hours
   Suspicion should be aroused by unusual business behavior outside of normal hours. For instance, you are not going to want your SQL ports (1433) open for traffic at 3am.
5. Utilize Simple Tools
   Give me a break, not everyone has tons of Splunk licenses laying around. Here are a few tips for starting out:
   • Filter logs using grep, awk, or power shell.
   • Export to CSV and import in Excel for pivot tables
   • Free log analyzers for SMBs (cheap and easy)
6. Document Findings
   Create a simple “log analysis template” of common threats or weird entries you found and mitigation steps taken. This habit has saved me all kinds of time.

Pro Tip: Don’t trust logs completely. Attackers do clear or tamper with logs sometimes. Which is why good firewall configuration produces logs and sends it all to a remote syslog server (we do this for clients at PJ Networks all the time).

Low-cost Security Services for Small Businesses

Here’s a confession: running P J Networks it would be easy to say “buy our firewall security.” But that wouldn’t be truthful because just like every business is unique, so is their budget and needs.

Here’s what I’ve learned: working with SMBs:

• You don’t require the 100k+ enterprise boxes. You just want something you can depend on and deal with. Yes, you can get good firewalls for less than 1000.
• Managed firewall services (eg, what we do) make sense if you don’t have full-time security staff.
• Don’t put money into AI-powered hype unless you know what the A.I. is doing. Most is marketing fluff. It is all about fundamentals of security.
• Then reinforce your firewall with periodic patching, strong password policies (I could rant forever about lame password policies, but here is my mantra: complexity + length beats complexity), and user training.
• Open-source solutions such as pfSense or OPNsense are free and visually impressive if you have (or can hire) a competent sysadmin.

At P J Networks we provide affordable but robust Security starting from less than a third of enterprise solutions so that the SMBs can defend themselves just like the big guys.

Quick Take

• Firewall logs may look like static, but they’re a window into your network’s vital signs. Listen carefully.
• Watch out for repeated suspicious blocks, abnormal ports and unusual outbound traffic.
• Pay attention to alerts, but set them wisely — avoid being inundated with false alarms.
• Simple command-line tools can do analysis without fancy dashboards.
• There are cost-effective solutions — you shouldn’t have to put your company in the poorhouse to be safe.
• And for crying out loud, don’t just leap onto some AI-powered security. The State of Your Tools: Know Before You Trust

Final Words From My Desk

From my 30 years of wrangling over the networks and firewalls, from modems on PSTN lines to zero-trust architectures for the banks—if I learned one thing is that if you don’t give a damn about your network (log) health, one day trouble is gonna come.

Or so my October 2023 data would suggest. But it’s essential. And with a little direction, even small businesses can be ahead of the curve — without investing in a full-time SOC or expensive hardware.

If you’re running a small biz, do it today: delve into those logs. Set up alerts. Ask questions. The voices in your firewall logs are not to be ignored — they are trying to tell you something.

And hey—if you want a hand? Let PJ Networks help you keep your network tight and your brain less cluttered. Because good security is not just for big enterprises. It’s for businesses such as yours that need peace of mind.

Stay safe out there,

Sanjay Seth
P J Networks Pvt Ltd