What Is External Attack Surface Management?

Why Is External Attack Surface Management (EASM) Important?

EASM provides organizations with a comprehensive view of the digital assets exposed to the internet, which are prime targets for cyberattacks. By continuously identifying and monitoring these assets, companies can proactively mitigate risks associated with vulnerabilities, misconfigurations, and shadow IT. Without EASM, organizations may be unaware of their true exposure, leaving critical gaps that attackers can exploit. 

Cyberattack vectors such as phishing, ransomware, and data breaches often target external-facing systems, making visibility into the attack surface essential for effective defense. For example, threat actors frequently exploit outdated software or unpatched systems connected to the internet to gain unauthorized access to sensitive information. EASM helps security teams identify these high-risk entry points before malicious actors do, allowing them to prioritize remediation efforts based on the threat landscape. 

Furthermore, regulatory requirements and compliance standards increasingly demand that businesses maintain a strong cybersecurity posture. EASM supports this by providing a continuous, real-time inventory of internet-exposed assets, ensuring that organizations can meet legal obligations while reducing the likelihood of costly breaches. Ultimately, it’s a foundational element of a broader risk management strategy, helping to protect against evolving cyberthreats in an increasingly interconnected world.

How Does EASM Work?

EASM works by continuously identifying domains, IP addresses, web applications, and cloud services, many of which may be unknown to the organization due to shadow IT, third-party services, or misconfigurations. EASM tools leverage automated discovery processes, such as reconnaissance and scanning, to map out the entire external-facing infrastructure and highlight potential entry points that attackers could exploit. 

Once the attack surface is mapped, EASM solutions analyze the discovered assets for vulnerabilities, misconfigurations, and compliance issues. It provides continuous monitoring and alerts for any changes or emerging risks, which enables security teams to prioritize remediation efforts based on risk levels and potential impact, reduce the organization's overall attack surface, and improve its security posture.

Here are some of the main capabilities of EASM:

• Asset discovery: EASM tools scan the internet to identify all external-facing assets, including those that may have been forgotten or not properly documented.
• Vulnerability assessment: After identifying assets, EASM performs automated vulnerability checks to detect weak points, such as outdated software or misconfigured systems.
• Risk prioritization: EASM tools categorize vulnerabilities based on their severity and potential impact, helping organizations to focus on the most critical issues.
• Continuous monitoring: By monitoring the attack surface in real-time, EASM ensures that new risks are quickly identified and addressed before they can be exploited by attackers.

Benefits of EASM

Here are some ways EASM allows organizations to stay one step ahead of cyber adversaries:

• Comprehensive visibility of external assets: EASM offers organizations a clear view of their entire digital footprint, including shadow IT and forgotten assets that can be potential entry points for attackers.
• Proactive risk identification: By continuously monitoring the external attack surface, EASM helps uncover vulnerabilities, misconfigurations, and exposures before they are exploited by threat actors.
• Improved security posture: With real-time insights into external risks, businesses can prioritize remediation efforts, effectively reducing the attack surface and strengthening overall security. 
• Enhanced incident response: EASM enables faster detection of external threats, allowing security teams to respond more efficiently and limit the potential impact of attacks. 
• Regulatory compliance support: Many industry regulations require organizations to regularly assess and manage their external vulnerabilities. EASM helps streamline compliance by providing continuous monitoring and reporting of external risks.

Challenges in External Attack Surface Management (EASM)

Managing your external attack surface is crucial, but it’s not without its hurdles. Many organizations face significant challenges when trying to gain visibility and control over their sprawling digital assets. Below are some of the most common obstacles that can complicate EASM efforts:

• Rapidly changing environments: As businesses expand or adopt new technologies, their attack surface grows and shifts. Keeping up with constant changes is a challenge, especially when new vulnerabilities can appear overnight.
• Alert fatigue: EASM tools often generate a high volume of alerts, not all of which are actionable. Sifting through noise to identify real risks can drain resources and lead to missed threats.
• Integration with risk management: EASM data is only useful if it’s integrated into a broader risk management strategy. Many organizations struggle to contextualize findings and align them with business priorities, leaving gaps in their security posture.

Internal vs. External Attack Surface Management

While EASM focuses on identifying, monitoring, and mitigating risks associated with an organization’s outward-facing digital footprint, internal attack surface management (IASM) deals with the threats and vulnerabilities that arise from within the organization. These could include insider threats, unpatched systems, misconfigurations, and gaps in internal security protocols. 

Both approaches are crucial for comprehensive risk management, but they differ in scope and focus, with EASM addressing external risks like exposed assets and shadow IT, while IASM tackles internal security lapses and privileged access risks.

Both internal and external attack surface management are integral to a robust cybersecurity strategy. While IASM helps secure the internal environment, EASM ensures that an organization’s external footprint is constantly monitored and protected from emerging threats. A comprehensive risk management approach should incorporate both, ensuring that organizations can defend against both external and internal vulnerabilities, reducing the risk of breaches and ensuring operational resilience.

Cyber Asset Attack Surface Management (CAASM)

Cyber asset attack surface management (CAASM) focuses on providing organizations with deep visibility and control over their internal assets, including devices, applications, cloud environments, and user accounts. While EASM concentrates on the external-facing attack surface, CAASM helps security teams identify, monitor, and manage vulnerabilities within the internal network. Together, these approaches offer a holistic view of the organization’s risk exposure, ensuring that both external threats and internal weaknesses are addressed. 

Using CAASM alongside EASM allows organizations to break down silos between external and internal asset management, creating a unified security strategy. By leveraging both, companies can proactively reduce risk, close attack vectors, and respond faster to emerging threats. This combination is essential for maintaining a robust security posture—one that not only mitigates external attacks, but also continuously monitors and secures internal infrastructure.

The Future of EASM In Cybersecurity

As organizations scale and digitize, their attack surfaces evolve, becoming more complex and difficult to secure. So, what does the future hold for EASM in the constantly shifting cybersecurity landscape? Here are five trends shaping the future of this space: 

Automation-driven threat detection 

As attack surfaces grow, automating threat detection is no longer optional. Organizations must plan to increase their investment in AI-driven security tools to better manage the growing complexity of their attack surfaces–a crucial shift as manual processes struggle to keep up with the scale of external threats.

Integration with broader risk management platforms

EASM is increasingly being integrated with unified risk management solutions, allowing organizations to correlate attack surface risks with overall business impact. This integration aligns with the broader trend of risk-based security, where decision-making is driven by business context, not just technical severity.

Cloud and third-party ecosystem expansion 

The expanding reliance on cloud services and third-party vendors is redefining the external attack surface. As a result, EASM tools that provide real-time visibility and assessment of third-party risks are becoming indispensable.

Focus on continuous, real-time monitoring

The demand for constant visibility into assets and vulnerabilities across an organization’s external attack surface is growing. According to IBM’s Cost of a Data Breach Report 2024, 1 in 3 data breaches involved shadow data, meaning that data in general is becoming more difficult to protect. Organizations must adjust their strategies to compensate.

Prioritization of risk-based decision-making

The future of EASM lies in risk-based security frameworks. As the external attack surface expands, companies are prioritizing vulnerabilities based on their potential business impact. Organizations will adopt risk-based vulnerability management, focusing on the most critical threats to business continuity.

How Does Zscaler Help?

Zscaler delivers EASM as a standalone, web-based, automated external attack surface analysis tool to help you and your organization:

• Understand trends and your exposure to internet-facing threats in near-real time
• Assess the severity of your vulnerabilities
• Continuously map them directly to your application assets and servers

Combining the broad Open Source Intelligence (OSINT) provided by Zscaler EASM with deep threat intel from Zscaler ThreatLabz, vulnerabilities can be found before they’re even disclosed as CVEs in NIST’s National Vulnerability Database (NVD). Leveraging the world's largest inline security cloud, the Zscaler Zero Trust Exchange platform can identify and fingerprint emerging threats in a small subset of customers and extend protection to all customers.

Why Are Zscaler and EASM Better Together?

• Exposure remediation: Pairing EASM findings with Zscaler Private Access is an effective tactic for securing OS and applications even when they cannot be patched due to factors such as being EOL, being fragile to change, or having uptime requirements.
• Phishing domain virtual takedown: EASM lookalike domain detection identifies malicious websites that are potentially abusing an organization's brand for typosquatting and phishing credential harvesting websites. These findings combined with Zscaler Internet Access allow for creating URL filtering policies that block access to the attacker hosted sites.
• Zero trust project hygiene: A critical phase of zero trust network access (ZTNA) projects is to validate that legacy systems (e.g., VPN concentrators) are retired after ZTNA adoption. EASM provides a continuous view of the internet-facing landscape to ensure that these assets are decommissioned to minimize the attack surface, realizing a core benefit of zero trust.
• Broad risk management: EASM acts as a feeder to the multifaceted Zscaler Risk360, where signals from across all threat origins (internal/external surfaces, inline traffic, out-of-band APIs, and more) are aggregated in a single view, together with guided investigative workflows and prioritized actions to prevent likely breaches.
• Competitive advantage: Armed with insights from your EASM, you can stay ahead of evolving threats and assure your clients about the safety of their data. Additionally, this is a potent tool for automating the footwork of M&A due diligence.

Schedule a custom demo with one of our experts to see how Zscaler helps you reduce the attack surface, eliminate lateral movement, and hide applications from the internet.