Your Attack Surface: How to Identify Your Company's Cyber Vulnerabilities

What Is an Attack Surface?

Your attack surface is the set of points on the boundary of your digital environment where an attacker can try to enter, cause damage, or extract data. It is not a single vulnerability or a specific technology. It is every potential point of weakness across your systems, your people, and your connections to third parties.

NIST, the US National Institute of Standards and Technology, defines an attack surface as "the set of points on the boundary of a system, a system component, or an environment where an attacker can try to enter, cause an effect on, or extract data from, that system, component, or environment."

Attack vectors that comprise your attack surface

Those “points on the boundary” are known as attack vectors: the specific paths or methods an attacker can use to breach your systems. For most SMEs and mid-market companies, attack vectors fall into three groups.

Your digital systems include every externally accessible part of your technology environment: your website, email platform, cloud applications, remote access tools, and any software connected to the internet. A misconfigured cloud service, an unpatched application, or an unsecured remote access tool can each provide an attacker with a way in.

‍Your people are a direct attack vector. Phishing, where an attacker tricks an employee into clicking a malicious link or sharing login credentials, is the most common method used to breach SMEs and mid-market companies. Employees with excessive access rights, or those using unsanctioned software that processes company data, also create points of weakness that can be exploited by malicious actors.

‍Your third-party relationships extend your attack surface beyond your own organization. Every supplier, vendor, or partner with access to your systems or data is a potential entry point. If they have access to your critical systems or data, an attacker may use a third-party to get to you.

How your attack surface expands over time

Every time your business adopts a new tool, onboards a new supplier, or you hire a new employee, your attack surface expands. Cloud applications, remote working tools, SaaS platforms, and third-party integrations all add new points where your systems are reachable from the outside. Over time, that accumulation of connections and dependencies means your attack surface is constantly changing. The risk exposure it represents is part of your cyber risk profile. And it should to be reviewed regularly as your business evolves.

Attack Surface vs. Vulnerability vs. Risk

These three terms are sometimes used interchangeably, but they describe different parts of the challenge of protecting your business.

Attack surface is the sum of all the points where an attacker could try to gain access to your assets.

Vulnerability is a specific weakness within that attack surface, e.g., unpatched software, a misconfigured cloud setting or lack of MFA.

Risk is the potential impact if a vulnerability is exploited, e.g., financial loss, business disruptions or reputational damage.

How to Identify Your Attack Vectors

Understanding your attack surface does not require technical expertise. It requires asking the right questions for each of the three groups of attack vectors above.

Identifying exposed systems and digital assets

Start by building a picture of every system, platform, and application your business uses that is accessible from outside your organization. For each one, the relevant questions are whether it is up to date, correctly configured, and actively monitored. Outdated software is one of the most consistently exploited vulnerabilities in SME assessments, and misconfigured systems are a common and avoidable entry point.

Shadow IT is a frequent blind spot. Software or services adopted by employees without going through a formal review process become part of your attack surface without anyone formally accounting for them.

Assessing employee and user access risks

Consider who has access to your systems and whether that access reflects what each person actually needs for their role. Limiting access rights to only what is necessary, a practice known as least privilege, reduces the number of potential entry points significantly. If an employee account is compromised, the damage an attacker can do is directly related to how much access that account had.

Phishing is the most common initial attack vector for SMEs. Employees who are trained to recognize and report suspicious emails are a meaningful line of defense.

Evaluating third-party cyber risk

For each vendor or partner with access to your systems, data, or revenue-generating processes, there are key questions you can ask.

• What systems or data does the third party access?
• What would happen to your operations if that third party was breached or went offline?
• Which of your revenue-generating processes depend on their access?
• Do they need that level of access?

Third-party access to your critical assets represents exposure that sits outside your direct control, and it needs to be understood and reviewed as part of any attack surface assessment.

Prioritizing and Acting on Your Attack Surface Assessment

Understanding your attack surface is the starting point. The next step is deciding where to focus.

How to prioritize cyber vulnerabilities by business impact

Not every vulnerability carries the same risk. Prioritization should be based on two factors: how likely a given vulnerability is to be exploited, and what the financial and operational impact would be if it were. A known software vulnerability on a system that processes customer payment data requires immediate attention.

A quantitative cyber risk assessment translates this prioritization into objective financial terms, so that decisions about where to invest can be evaluated on the same basis as any other business decision.

When a professional attack surface assessment is needed

An internal vulnerability assessment will expose the most obvious gaps. It has limits, however. A business leader conducting a self-assessment cannot identify vulnerabilities they do not know to look for, and cannot objectively evaluate the controls their own team has put in place.

An independent assessment of your cyber risk can provide critical recommendations about how to better protect your business and strengthen your resilience. For organizations subject to NIS2 or DORA, or those required to demonstrate their security posture to enterprise customers or insurers, an independent assessment is increasingly a practical requirement.