When Target granted network access to an HVAC contractor for remote temperature monitoring, they never imagined it would trigger a $290 million breach. Attackers simply stole the vendor's credentials and pivoted into Target's payment systems, compromising millions of customer records.

This pattern repeats across industries. Third-party breaches now account for the majority of security incidents, with vendor email compromise becoming attackers' preferred entry point. These sophisticated threats consistently exploit one truth. Organizations extend trust to hundreds of vendors while maintaining visibility. This article highlights five mistakes that transform routine vendor relationships into existential threats.

Vendor relationships extend attack surfaces to networks beyond organizational control. Third-party breaches occur when attackers compromise vendors and pivot into customer networks, with an NPR article citing that 59% of all data breaches and 53% of third-party incidents concentrated in North America alone. These attacks exploit business-to-business connections, stealing data while it's in supplier custody.

Fragmented ownership across procurement, IT, and business units creates visibility gaps while implicit trust develops after contract signing. Attackers exploit this trust through vendor email compromise, hijacking legitimate threads to redirect payments or steal credentials.

Once inside vendor systems, threat actors leverage existing network access to infiltrate multiple downstream customers simultaneously. Without continuous oversight of suppliers and communications, these blind spots remain prime targets for scalable attacks.

Vendor breaches create significant financial damage across operations and brand equity. With the global average breach cost at $4.4 million according to IBM Cost of a Data Breach Report, 2025, vendor-related incidents typically exceed this baseline due to complex multi-party remediation and detection delays. Additionally, organizations that use extensive AI in security save $1.9 million compared to those without these solutions.

Direct expenses include forensics, legal counsel, and customer notification, while regulatory penalties under GDPR can reach 4% of global revenue. Without proper controls, vendor breaches transform from manageable incidents into existential financial threats.

Uniform risk assessments obscure dangers from high-access suppliers handling sensitive data. Cloud providers pose fundamentally different threats than office suppliers, yet identical questionnaires miss critical gaps. Tiered classification by data access and system reach targets scrutiny effectively.

Organizations using three to five risk tiers reduce assessment time while uncovering more vulnerabilities. Tier 1 vendors receive continuous monitoring and targeted audits; lower tiers get streamlined checks. Dynamic scoring ensures effort matches exposure while keeping low-risk relationships frictionless.

Organizations missing communication baselines fail to detect early compromise indicators. Attackers surface through subtle anomalies: emails outside normal hours, tone shifts, or urgent banking updates that annual reviews miss. A vendor who typically sends invoices on the fifteenth suddenly requests payment on the third; accounting departments, which usually process requests from specific email addresses, now receive messages from slightly altered domains; routine purchase orders arrive with new "expedited processing" language never seen before.

The solution requires establishing baselines for high-risk vendors, including typical send times, domains, and payment instructions. Behavioral analytics create profiles tracking communication frequency, attachment types, and even writing style. Automated monitoring flags deviations immediately, while multifactor authentication and DMARC prevent initial compromise. When patterns break, security teams receive alerts before funds are transferred or credentials are leaked.

VEC hijacks supplier trust, converting routine payment requests into multimillion-dollar losses. Attackers study conversations, spoof domains or compromise mailboxes, then redirect wire transfers.

Enforce DMARC alignment for partner domains, require multifactor authentication on vendor portals, and deploy behavioral AI profiling for each vendor's standard patterns. First deviations trigger immediate holds on funds, transforming blind spots into monitored perimeters before cash moves.

Encrypted databases mean nothing when attackers hijack communication layers moving data. Email, chat, and collaboration tools that store credentials and invoices remain exposed as organizations focus on storage security. Threat actors spoof domains, poison shared workspaces, and redirect payments, knowing few teams monitor behavioral shifts.

Secure communication channels with end-to-end encryption and multifactor authentication across vendor interfaces. Establish behavioral baselines and alert on anomalies such as misspelled domains, tone changes, and off-hour requests. Require vendors demonstrating secure email configurations (SPF, DKIM, DMARC) during onboarding.

Vague contractual language, such as "reasonable security measures," creates loopholes when breaches occur. Generic liability caps remove accountability incentives, while hold-harmless provisions push the financial burden back onto the vendor despite vendor negligence.

Specify required frameworks (ISO 27001, SOC 2), mandate 24-hour breach notification, and preserve audit rights. Move beyond paperwork to evidence-based assurance: quarterly penetration tests, continuous attack surface monitoring, and accessible immutable logs.

Additionally, budget these activities upfront; underfunded programs default to reactive firefighting. Regular validation prevents multi-day outages from hitting unmonitored peers.

Abnormal's VendorBase technology revolutionizes vendor risk management by detecting anomalies in supplier interactions using behavioral AI. API-based deployment integrates smoothly without modifying MX records, while behavioral modeling reveals hidden risks.

Additionally, cross-channel protection strengthens defenses across all communication layers, resulting in fewer false positives and enhanced attack prevention. Industry recognition and customer success validate the platform's capability to transform vendor relationships from blind spots into managed partnerships.

Ready to eliminate vendor blind spots before they become breaches? Get a demo to see how Abnormal can protect your organization from sophisticated vendor-based attacks.