Application Programming Interfaces (APIs) have revolutionized connectivity and data sharing, but their pervasiveness has also created a new set of cybersecurity challenges. As businesses continually expand and update their applications, they often overlook APIs left behind by developers — shadow and zombie APIs — that continue to operate undetected. These abandoned APIs become silent risks, operating in the background, unknown to most security teams, and they can pose serious security threats.
What are Shadow and Zombie APIs?
Shadow APIs are APIs that exist outside of the company’s known inventory, often created by development or product teams to meet project demands but not officially documented or tracked. This lack of oversight means that shadow APIs typically bypass standard security policies and access controls.
Zombie APIs refer to APIs that were initially designed for a purpose but were later deprecated, forgotten, or replaced. Instead of being fully retired, they remain active within the infrastructure, often with outdated security protocols, becoming prime targets for attackers.
Together, shadow and zombie APIs represent unseen vulnerabilities that make a company’s attack surface larger and more complex than it may first appear.
Why are Shadow and Zombie APIs Dangerous?
Allowing shadow or zombie APIs to accumulate within an organization’s infrastructure is a huge risk for three main reasons:
1. Unmonitored Data Exposure
APIs often transmit sensitive data, but shadow APIs may lack encryption or proper access controls to protect data and keep it from leaking outside the organization. According to the Ponemon Institute, some 58 percent of respondents say APIs are a security risk because they expand the attack surface across all layers of the technology stack and are now considered organizations’ largest attack surface. Shadow APIs bypass standard security protocols and therefore contribute to this expanded attack surface.
And with regulations like GDPR and CCPA mandating strict data protection and audit trails, Shadow APIs, which are undocumented and untracked, pose significant compliance risks as they might expose personal or financial information without proper monitoring.
2. Increased Attack Surface
Shadow and zombie APIs expand the attack surface, making it difficult for security teams to enforce API security policies across all endpoints. Attackers target these APIs precisely because they are out of sight, exploiting them to gain unauthorized access to the infrastructure.
According to a Palo Alto Networks survey, 92% of organizations experienced an API-related security incident in the last year. Shadow APIs, by being out of security’s reach, contribute disproportionately to this statistic, as attackers actively seek out overlooked and under-protected entry points. Moreover, only 10% of organizations fully document their APIs, according to a 2023 report from Enterprise Management Associates (EMA).
3. Legacy Security Risks
Zombie APIs are especially vulnerable because they often use outdated security protocols, encryption methods, or authentication processes. Many still rely on basic API keys instead of modern protocols like OAuth 2.0, making them easy targets for credential theft or brute force attacks.
Furthermore, without regular maintenance, zombie APIs often contain known vulnerabilities, essentially harboring ticking time bombs due to outdated or deprecated APIs left in production environments. Attackers take advantage of these unpatched vulnerabilities, using them to infiltrate the system or move laterally within the network.
How Attackers Exploit Shadow and Zombie APIs
Attackers frequently scan enterprise environments for these unmonitored APIs, as they offer a low-effort path into otherwise secure systems. Common tactics include:
- Credential Stuffing: Since zombie APIs often use outdated authentication, attackers can employ credential stuffing — using leaked passwords across different services — to gain unauthorized access.
- API Enumeration: Attackers use enumeration techniques to discover shadow APIs by making trial-and-error requests. Once identified, these APIs become launchpads for data exfiltration, account takeover, and other attacks.
- Automated Exploits: Bots designed to find misconfigured APIs scan for endpoints without proper access restrictions. If shadow or zombie APIs allow excessive permissions, they’re prime targets for automated attacks that go undetected for long periods.
Bringing Shadow and Zombie APIs to Light
Given the hidden nature of shadow and zombie APIs, proactive management is key to addressing the problems posed by them. Here are best practices to help companies protect themselves:
Automate API Discovery and Cataloging
Companies need to deploy API discovery tools that automatically scan for all active APIs, including those not documented or officially sanctioned. By implementing a comprehensive inventory of all active APIs and prioritizing their maintenance, organizations can drastically reduce shadow API risks.
Implement Continuous Monitoring and Risk Scoring
Once APIs are cataloged, continuous monitoring ensures that any unusual access patterns, excessive data requests, or suspicious behavior are flagged. Many advanced tools use machine learning to detect abnormal usage, helping security teams to respond before attackers cause significant damage.
Enforce Strict API Decommissioning Policies
Proper API lifecycle management is critical to prevent zombie APIs from lurking in production. When an API is no longer needed, it must be decommissioned and removed from the system entirely. Implementing automated deprecation procedures minimizes the risk of forgotten APIs.
Regular Audits and Compliance Checks
Routine security audits focused on APIs ensure that all active endpoints comply with current security standards and regulatory requirements. Regular audits can help identify and remediate security gaps, particularly in shadow and zombie APIs that were created without proper oversight.
Conclusion: APIs as Silent Risks
APIs, as silent enablers of connectivity, are also silent risks when left unmonitored. As organizations become more API-dependent, shadow and zombie APIs will continue to pose security challenges unless proactively managed. By understanding and addressing these threats, companies can ensure that their APIs work for them, not against them, bolstering overall security and resilience in an increasingly interconnected world.
To learn more about how Salt can help protect your organization from the hidden threats of shadow and zombie APIs, schedule a demo today!