What is a supply chain attack and how can you protect your business?

The technology your business relies on does not stop at the edge of your own network. Cloud services host data and applications, software suppliers issue regular updates, managed service providers access customer environments, and third-party vendors support critical business processes.

That makes modern businesses more efficient, but also more interconnected. A security weakness elsewhere in your supply chain can quickly become your problem.

A supply chain attack exploits one of these trusted relationships. Instead of attacking a targeted organisation directly, threat actors compromise a supplier, service provider or software component and use it as a route to their real target. The UK’s National Cyber Security Centre (NCSC) warns that supply chains can be large and complex, with vulnerabilities introduced or exploited at any point. It also describes the trend of attackers exploiting weaknesses in supply chain security as real and growing.

For businesses, the challenge is therefore bigger than securing your own systems. You also need to understand who and what you depend on, what access those relationships create, and what would happen if a trusted supplier were compromised.

If you are reading this because your organisation has experienced a cyber incident and is unsure how to respond, contact Zensec immediately.

What is a supply chain attack?

A supply chain attack occurs when attackers use a third-party dependency to reach another organisation. That dependency could be a software supplier, cloud service, managed service provider, third-party vendor, hardware supplier or even a component within the software your organisation uses. The attacker is looking for an easier route into the target.

Consider a managed IT provider with privileged access to customer systems. If threat actors compromise the provider’s credentials, they may attempt to use that legitimate access to gain unauthorised access to a customer’s environment. Software creates another route. Businesses routinely install software updates because they trust the software provider delivering them. If an attacker can compromise that process and insert malicious code into an apparently legitimate update, that trust can work in the attacker’s favour.

This is why traditional security controls are only part of the answer. An organisation may have strong defences around its own network while still being exposed to supply chain vulnerabilities that originate elsewhere. According to the NCSC, most organisations rely on suppliers for products, systems and services, yet many businesses lose sight of the cyber security risks those relationships create. Supply chain security is ultimately about understanding that extended environment and controlling the risks as far as reasonably possible.

How do supply chain attacks happen?

Not every supply chain attack looks the same. A software supply chain attack targets part of the process used to create or distribute software. Threat actors may look for weaknesses in software development tools, third-party libraries, open source software or software update mechanisms.  If attackers succeed in injecting malicious code into legitimate software, downstream customers could install the compromised component believing it to be safe. A single compromise can therefore potentially provide access to many organisations.

Software vulnerabilities can also create opportunities. The modern software supply chain contains numerous products and dependencies, and a vulnerability affecting a widely used component can expose organisations that may not even realise they rely on it. Other attacks focus on trusted access rather than software.

A third-party supplier may have remote access to the company’s systems, while a cloud or service provider might process sensitive data or support essential operations. Compromise the provider, and attackers may have a potential route towards its customers. Supply chain risk is not limited to software either. Hardware supply chain attacks can involve devices or components being tampered with during manufacturing or distribution, an important consideration for some high-value targets and critical infrastructure.

Then there are techniques such as watering hole attacks, where threat actors compromise a website or resource regularly used by their intended targets. Different techniques create different risks, but they share one fundamental characteristic: the attacker takes advantage of an existing relationship or dependency rather than approaching the target through the front door.

Why are supply chain attacks such a concern for businesses?

The difficulty is visibility. Most organisations know which employees have access to their network. Understanding every external dependency can be considerably harder. A trusted vendor may rely on another software provider or cloud service. That provider could use third-party software, development tools or open source libraries of its own. Before long, your digital supply chain extends far beyond the suppliers listed in procurement records.

The NCSC recommends supply chain mapping to give organisations an up-to-date understanding of their network of suppliers. The aim is to understand who suppliers are, what they provide and how they provide it, allowing cyber risks to be managed more effectively. This matters because not all suppliers create equal risk. A provider with no access to your systems or data is a very different proposition from a third party with privileged access to critical infrastructure. Likewise, a software component installed on hundreds of end user devices creates a different risk from an isolated service.

A supply chain compromise could lead to data theft, unauthorised access, malware deployment, operational disruption or a wider data breach. For software suppliers and service providers with numerous customers, the effects can also spread downstream. That changes the question businesses need to ask. It is not simply, “Do we trust this supplier?”, it is, “If this supplier were compromised, what could an attacker reach?”

How can you protect your business from supply chain attacks?

You cannot remove every third-party dependency, nor can you guarantee that a trusted supplier will never suffer an incident. The goal is to understand where the greatest supply chain risks exist and limit the damage if a compromise occurs.

Start with your most important suppliers. Identify which third-party vendors have access to sensitive data, critical systems or privileged accounts. Look at the software deployed widely across your organisation and the cloud services or service providers your essential operations depend on. This is where supply chain mapping becomes useful. The NCSC recommends maintaining an up-to-date picture of supplier dependencies so organisations can make better risk-based decisions and respond more effectively to supply chain incidents.

Once you understand the dependencies, focus security measures according to risk. For important vendors, that may involve reviewing their security posture, vulnerability management, incident response processes and relevant security certifications. The NCSC also points to Cyber Essentials as one way of gaining assurance that suppliers have implemented fundamental technical controls against common attacks.

Controlling access is equally important. Third-party providers should have only the permissions required to perform their role. Applying least privilege access, using multi-factor authentication and removing old supplier accounts can reduce the opportunities available to an attacker who compromises a vendor.

The same thinking applies to software. Organisations should manage known software vulnerabilities, keep third-party software appropriately updated and ensure software updates come from trusted sources. Businesses developing their own software should also protect development environments and consider controls such as code signing to help verify software integrity.

Finally, prepare for the possibility that prevention fails. Continuous monitoring of accounts, endpoints and network traffic can help security operations teams identify unusual activity. Endpoint detection can provide further visibility across user devices, while incident response plans should consider what happens if an important supplier reports a compromise.

Could you identify every system using its software? Could you disable third-party access quickly? Would you know what sensitive data was potentially exposed? Those practical questions are what turn supply chain security from a procurement exercise into effective cyber risk management.

Building stronger supply chain security

Businesses cannot operate effectively without third parties. Software suppliers, cloud services and specialist providers are fundamental to modern operations, so avoiding external dependencies altogether is neither realistic nor desirable. The priority is understanding the trust those relationships create.

Know which suppliers are critical. Understand what systems and sensitive data they can access. Limit privileges appropriately and monitor important connections. Keep software updated and prepare your incident response processes for a situation where the incident begins with someone else.

The NCSC acknowledges that it is not possible to completely eradicate supply chain attacks. Its guidance instead encourages organisations to understand their risks and introduce security measures proportionate to the likelihood and potential impact of those risks. That is a much more realistic goal.

A trusted third-party vendor can still suffer a cyber attack. Strong supply chain security ensures that trust does not automatically translate into uncontrolled risk. Zensec helps organisations identify vulnerabilities, understand cyber risk and strengthen their overall security posture. If you are concerned about the risks created by third-party dependencies, assessing who can access your critical systems and how well that access is controlled is a sensible place to start.