What is an Attack Surface Assessment?

Introduction

Cybersecurity jargon can feel like it’s designed to keep business leaders in the dark. 

But if there’s one term you should be familiar with, it’s attack surface. 

Why? 

Because it’s everything a hacker can use to get into your systems, and you can’t defend what you don’t know exists.

An Attack Surface Assessment is the process of identifying, mapping, and understanding every possible way an attacker might gain access to your organisation’s digital or physical assets. 

And no, it’s not just for enterprise giants. Whether you’re running a law firm, a fintech start-up, or any other type of business, your attack surface is growing by the day.

If you’re struggling to decipher tech jargon, check out our tech terms glossary.

The Basics: What Counts as an “Attack Surface”?

Think of your attack surface like the entry points to a castle (if you’ve read any of our other blogs, you’ll know that we love using castles for cybersecurity analogies). 

When planning to attack a castle, the attacking force will analyse every single aspect of the castle to understand its strengths and weaknesses. Then, it will exploit these weaknesses to gain entry.

For a castle, the attack surface refers to its curtain walls, inner keep, towers, tunnels, moats, guards, windows, gutters, bridges, location and terrain (to name a few). 

For businesses, every open port, misconfigured server, forgotten subdomain, or even a compromised employee’s login is a potential weak spot in the castle that is your business. 

Broadly, your attack surface includes:

• External-facing assets: Websites, web apps, IP addresses, VPNs, cloud environments.
• Internal systems: Servers, databases, legacy systems, intranet applications.
• Human factors: Employee credentials, shadow IT, social engineering vectors.
• Third-party vendors: APIs, integrations, and external platforms you rely on.

Hackers have even been known to use floor plans of offices found freely online to help them gain entry to businesses. All of these things can be found during a attack surface assessment (but, I’m getting ahead of myself a touch there).

According to IBM’s Cost of a Data Breach Report 2023, organisations with complex digital environments had an average breach cost of $5.28 million, compared to $3.87 million for those with smaller, well-managed attack surfaces. 

That’s a 36% difference caused purely by a lack of awareness around the true nature of your attack surface.

Want to learn more about attack surfaces? Check out our guide.

Why Are Attack Surfaces Growing?

Put simply, cloud adoption, hybrid work, and digital transformation have exploded post-COVID, as we’re all aware.

And while that’s great for flexibility, growth, and employee satisfaction and productivity, it also means more devices, more endpoints, and more gaps. I.e., a bigger attack surface. 

A 2024 report by Trend Micro found that 73% of IT leaders believe their organisation’s attack surface is “spiralling out of control”.

Meanwhile, Gartner predicts that by 2026, 70% of organisations will prioritise attack surface management as a top security priority, up from just 25% in 2022.

In short, you’re not imagining it. Your attack surface really is expanding, and fast.

So, What Happens During an Attack Surface Assessment?

An attack surface assessment is a structured process designed to answer one core question: How exposed are we, really?

Here’s what it usually involves:

1. Asset Discovery

This is the digital version of walking around your perimeter and looking for doors you didn’t know existed or doors you knew existed, but didn’t realise were unlocked. This includes known assets (your company website, for example) and unknown ones (a dev server or remote management tools someone spun up in 2021 and forgot about).

We have a case study dedicated to an issue just like this one that we found for an international oil and gas supplier!

2. Risk Prioritisation

Not all entry points are equal. A misconfigured S3 bucket holding client data? High risk. A test login portal with no live connection? Lower. The assessment will grade your exposure and highlight your riskiest points of entry. 

Apologies for the tech jargon there. Put really simply, an S3 bucket is a type of storage container within Amazon’s Simple Storage Service. Not something you want hackers breaking into!

3. Exposure Analysis

This phase looks at how your assets are actually seen from the outside, including from a hacker’s perspective. That means checking for open ports, weak credentials, exposed APIs, and outdated software versions.

4. Remediation Roadmap

Finally, you’ll get a report with recommended actions. This might include patching vulnerabilities, removing unused services, hardening systems, or changing default configurations.

What Are the Benefits of an Attack Surface Assessment?

The most obvious benefit is reducing your risk of a breach. But it also does a lot more.

• Gives you visibility over shadow IT and unmanaged assets
• Improves compliance with ISO 27001, NIST, GDPR, and other frameworks
• Saves money on reactive incident response
• Provides clarity for board-level reporting on cyber risk
• Larger scope means the assessment is more realistic compared to other types of cybersecurity test/assessment.

And perhaps most importantly, it helps you sleep at night knowing you’ve shut every digital window you didn’t know was open.

Real-World Example: How One Missed Asset Cost Millions

In 2021, the Colonial Pipeline attack was traced back to a single compromised VPN account that lacked multi-factor authentication (MfA). 

The attackers didn’t use zero-day exploits or brute force. 

They walked right in through the front door (or rather, an exposed point in the company’s attack surface). 

The result? 

A $4.4 million ransom, plus nationwide fuel shortages across the US East Coast.

It’s a stark reminder that you don’t need hundreds of vulnerabilities. You just need one.

Should You Get an Attack Surface Assessment?

If you:

• Rely on cloud infrastructure
• Work with remote or hybrid teams
• Use third-party platforms
• Are subject to regulatory requirements

…then yes, 100%. And ideally, not just once. Like a MOT for your business, attack surface assessments should be conducted regularly, especially after major infrastructure changes.

Are Attack Surface Assessments the Same as External Infrastructure Penetration Tests?

No, and here’s why. 

All attack surface assessments include external infrastructure tests, whereas external infrastructure tests focus solely on the IP addresses associated with your network. 

Over the years, we’ve found that when people ask for an external infrastructure penetration test, they often expect an attack surface assessment, unaware that the two are entirely different.

As you’d expect, with attack surface assessments being significantly more thorough, they are more expensive than external infrastructure tests… but not by as much as you’d imagine.

Obviously, this varies depending on the size of the client (i.e., the size of their attack surface), but typically, our attack surface assessments usually take only one or two days longer than a standard external infrastructure penetration test.

Want to learn more about external infrastructure penetration tests? Check out our service page or our comprehensive guide.

Conclusion

Most breaches don’t start with someone kicking down the front door. 

They begin with something you forgot existed—a neglected API, a reused password, or a small error that no one noticed. 

An attack surface assessment doesn’t just give you a list of vulnerabilities. It gives you a full breakdown of what a potential attacker will see when looking at your business.

And in cybersecurity, understanding your attack surface is one of the most important things when it comes to preventing cyberattacks.

Are you looking to conduct an attack surface assessment? Contact us today.

Feel free to check out more of our educational articles.