Third-Party Access Governance: How to Prevent Supply Chain Attacks

Among CEOs of highly resilient organizations, 78% say third-party and supply chain vulnerabilities are their #1 barrier to becoming cyber resilient.  

The issue isn’t that third parties can get in – the gig economy and SaaS integrations are only becoming more central to enterprise operations. But when threat actors can abuse third-party credentials to log in and effectively access 100% of your environment within two hops, third-party access often introduces an untenable level of business risk in the name of operational ease, and it can only be addressed at the architectural level. 

We’ll explore how excessive third-party access can lead to supply chain attacks, the governance challenges that typically stand in the way of cyber resilience, and five best practices to limit third-party access and keep every attack contained automatically.  

Key Answers  

• Why is third-party access risky? Third-party identities (whether human or machine) are typically provisioned once and rarely re-evaluated. A vendor login, a contractor’s VPN account, or an OAuth token connecting SaaS platforms often carries far more reach than is operationally necessary; if that identity is compromised, threat actors inherit the existing access. 
• How does a Zero Trust architecture help contain supply chain attacks once an attacker is inside? A Zero Trust architecture treats every connection as potentially risky; foundational Zero Trust strategies like microsegmentation and identity-based access controls ensure that third-party identities are constrained to a pre-defined scope and unable to move laterally. This means that attacks are automatically contained to the initial point of compromise, regardless of how they start.  
• What are best practices for preventing supply chain attacks? Supply chain attacks are inherently difficult to detect or block at the perimeter, so the strongest defense is limiting the potential impact of a breach to prevent enterprise-wide compromise: implement microsegmentation to block lateral movement; enforce identity-based access controls for human, machine, and AI identities; modernize secure remote access by replacing VPNs with ZTNA; apply just-in-time MFA for all privileged access; maintain real-time visibility into what every third-party connection can reach.  

What Is a Supply Chain Attack?  

A supply chain attack is a cyberattack that targets a trusted third party – such as a software vendor, service provider, SaaS integration, or contractor – and exploits existing access to breach a target environment. 

Third-Party Breach vs. Supply Chain Attack: What’s the Difference?  

While third-party breaches and supply chain attacks are related, they describe incidents with different levels of impact:  

• A third-party breach refers to any cyber incident where a vendor, contractor, or partner is compromised via a third-party attack vector – even if that compromise never reaches an organization’s environment.  
• A supply chain attack is where threat actors leverage a third-party breach as a steppingstone to impact downstream users or clients.  

Practically speaking, the third-party breaches that make headlines are usually supply chain attacks, but not every third-party breach escalates into a supply chain attack.  

How Third-Party Compromise Threatens Business Continuity  

When a vendor, contractor, partner, or third-party app connects to an enterprise environment, they inherit some level of trust – in most networks, that trust is broad by default. Third-party connections are often granted access that matches the broadest operational need the relationship might ever require, and those permissions tend to accumulate over time.  

Standing privileges, persistent connections, and broadly reachable internal systems create conditions where a single compromise upstream can rapidly expose an entire environment downstream, and attackers know it. Almost half of the breaches investigated for Verizon’s 2026 DBIR Report involved a third party – a 60% increase year-over-year.  

Real-World Examples: Supply Chain Attacks via Third-Party Compromise  

When a third party is compromised, attackers can move laterally to target environments directly via stolen credentials or inject malicious code into a trusted system to execute software supply chain attacks. Some of the most well-known examples of supply chain attacks illustrate how a third-party breach can ultimately threaten business resilience:  

• Target (2013): Target experienced a massive data breach, impacting roughly 110 million customers, when a third-party HVAC vendor’s credentials were compromised. Although Target’s systems did issue multiple alerts regarding malicious activity, Target’s SOC disregarded the alerts amid a sea of noisy warnings. Alert fatigue contributed directly to the breach’s scale, which ultimately shone a light on the risk of supply chain attacks for the industry.  
• SolarWinds (2020): In one of the largest supply chain attacks to date, adversaries injected a backdoor into one DLL in SolarWinds’ Orion product, which was then delivered through software update to roughly 18,000 organizations. From there, attackers chose specific organizations to compromise further, typically leveraging credentials that allowed them to use legitimate remote access (such as VPNs and RDP servers), which largely hid the attack from detection and response tools.   

In both cases, implicit third-party trust materially enabled the supply chain attack’s ultimate impact. 

Third-Party Vulnerabilities: Governance Challenges  

Most organizations address third-party access risks by layering on familiar hurdles: security assessments are completed before onboarding, access requires authentication, sessions are logged, and contracts may even include security requirements. But traditional governance models weren’t built to keep pace with how many vendors, contractors, and integrations now touch the average enterprise environment, creating an evolving set of challenges for security teams:  

• Exposure accumulates faster than security gaps are remediated: According to the 2026 Verizon DBIR, it takes almost eight months to resolve just 50% of weak passwords and permission misconfigurations for third parties, and 37% of third parties have MFA disabled on at least one admin account, despite a policy requiring it. With new vendors and integrations added constantly in dynamic enterprise environments, those gaps compound into a complex web of third-party risk.  
• Third-party identities lack ongoing oversight: Research shows that many organizations lack a unified view of SaaS connections and vendor integrations, meaning they can't quickly answer where a given vendor has access, what that access actually enables, or how to revoke it cleanly if needed. Since most third-party governance is front-loaded, a lack of ongoing visibility leaves security teams blind to the full scope of risk exposure.  
• Integration ownership erodes over time: Vendor relationships and third-party integrations often outlast the tenure of the person or team that set them up, but third-party access is rarely revisited after it’s provisioned. In one Unit 42 investigation into a single SaaS integration, researchers uncovered nearly 100 additional third-party integrations connected to the same platform – many dormant, unmonitored, or tied to employees that had already left the organization.  

Governing third-party access at the entry point without determining what happens inside the network – after initial access – leaves a structural gap between enforcement and real risk exposure.   

Tightening the perimeter without constraining internal reachability leaves the most consequential part of the attack chain largely unaddressed. Closing that gap requires shifting governance from a point-in-time access decision to a continuous architectural constraint. 

5 Best Practices for Third-Party Access Governance and Supply Chain Attack Containment  

Enterprises must govern what any third-party identity can reach, keep that governance current as the network evolves, and proactively limit internal access paths. Applied consistently across vendors, contractors, and integrations, a closed-by-default architecture drastically reduces the reach of any compromised identity, regardless of how the initial breach occurs.  

1. Implement Microsegmentation for Proactive Breach Containment  

Microsegmentation isolates every asset inside its own secure zone. When internal access paths are closed by default and only available if there’s a specific business need, unauthorized lateral movement is prevented structurally, and the blast radius of any breach is automatically constrained. A granularly segmented architecture removes the dependency on detection to contain supply chain attacks by proactively cutting off the internal trust and reachability that attackers rely on. 

2. Enforce Identity-Based Access Controls  

Third-party access should be narrowly scoped to what’s operationally necessary with enforcement tied to identity. This is a fundamentally different posture than logging and monitoring broad access; instead, a compromised vendor credential doesn't open up access to the entire network – it opens a narrow, policy-defined slice of it. When layered on top of a granularly segmented network architecture, identity-based controls effectively mitigate the identity weaknesses that play a material role in nearly 90% of cyber incidents.  

3. Replace VPN with a Modern Secure Remote Access Solution 

VPN and RDP access remain the top connection types sold by initial access brokers, accounting for the majority of pre-compromised access available on underground markets. This is the same pattern that made SolarWinds so difficult to detect – because third-party remote access is treated as an already-trusted route, it’s a dependable path into target environments for attackers. A modern secure remote access solution should replace standing VPN tunnels with access granted based on identity and context, combining the security of ZTNA with the speed of VPN. This way, remote third parties get the access they need but the rest of the network stays invisible by default.  

4. Add Just-in-Time (JIT) MFA for Privileged Access  

Persistent privileged access to sensitive systems leaves organizations exposed via compromised credentials, even if identity-based access controls are enforced – and traditional MFA doesn’t always close that gap. Mandiant’s 2026 M-Trends Report found that stolen OAuth and refresh tokens often remain valid after logout, allowing attackers to hijack sessions without triggering an MFA alert at all. By implementing network-layer MFA on all privileged pathways, enterprises can enforce just-in-time verification that opens privileged access temporarily for pre-approved identities.  

5. Maintain Real-Time Network Visibility That Informs Dynamic Access Policies  

Periodic reviews can’t keep pace with how quickly vendor relationships and integrations change; OAuth tokens accumulate across SaaS integrations, API keys get issued and forgotten, and vendor accounts outlive the contracts that authorized them – before security teams can effectively govern third-party access, they need to fully understand it. Enterprises should maintain a real-time network map that shows all access paths and identity activity, enabling adaptive policy creation and enforcement grounded in observed network behavior.  

Strengthen Supply Chain Resilience: Build a Closed-by-Default Architecture with Zero Networks 

Modern business operations require third-party connections, but that doesn’t mean enterprises have to accept an untenable – and often hidden – level of third-party risk exposure. Zero Networks enables security teams to build a network architecture that defines what any third party can reach, how long elevated access persists, and how quickly it can be revoked, shifting third-party and supply chain vulnerabilities from a top resilience hurdle to an easily surmountable one.   

With automated, identity-based microsegmentation, Zero governs reachability based on the identity of every third party, closing access paths by default without slowing the pace of business. Patented network-layer MFA extends just-in-time verification to the privileged protocols and admin pathways that traditional MFA leaves exposed, while our modern secure remote access solution combines the speed of VPN with the security of ZTNA, delivering third-party access to pre-approved apps and services only.  

The result is a self-defending architecture where a compromised vendor credential, hijacked integration token, or overprivileged service account has nowhere to go, ensuring third-party compromise doesn’t escalate into disruptive supply chain attacks. See for yourself how Zero Networks narrows third-party trust to what’s actually needed and proactively contains any attack – request a demo.