External Attack Surface Management

EASM provides three critical benefits for organizations. First, it gives you complete visibility into unknown assets across your organization, including subdomains, APIs, and shadow IT that traditional asset management might miss. Second, it enables proactive vulnerability management by identifying security issues in public-facing assets before attackers exploit them. Third, it supports risk prioritization by providing context about which vulnerabilities pose the greatest threat based on exposure and potential impact. External attack surface management becomes essential as organizations expand their digital footprint through cloud services and remote work.

Internal attack surface includes assets within your corporate network that attackers could exploit after breaching the perimeter. This covers servers, databases, and systems behind your firewall. External attack surface, in contrast, includes internet-facing assets visible to anyone online. These include websites, cloud services, domains, and APIs that can be accessed from outside your network. External attack surface management focuses on reducing vulnerabilities that outside threats can exploit, while internal attack surface management secures assets from lateral movement after an initial breach.

The external attack surface is all digital assets and services your organization operates that are accessible from the internet. This includes your main websites, subdomains, cloud applications, APIs, email servers, and any third-party services connected to your systems. It also includes forgotten or unknown assets like old development servers, misconfigured cloud storage, or abandoned domains that still point to your infrastructure. The external attack surface grows as organizations adopt cloud services, remote work tools, and third-party integrations. CISA emphasizes the importance of managing external dependencies as part of operational resilience.

An EASM tool is software that automatically discovers, maps, and monitors your organization’s external attack surface. These tools continuously scan the internet to find assets associated with your organization, including known and unknown domains, subdomains, cloud services, and exposed ports. They check for vulnerabilities, misconfigurations, expired certificates, and other security issues. EASM tools provide real-time visibility into your external footprint and alert you when new assets appear or security risks are detected. They help security teams maintain an accurate inventory of internet-facing assets and prioritize remediation efforts.

External attack surface management is critical because you can’t protect what you don’t know exists. With cloud services and remote work, companies create new digital assets faster than ever, often losing track of them. This creates dangerous blind spots that attackers exploit. Traditional asset management can’t keep up with modern attack surfaces that change daily. Organizations become vulnerable to attacks through unknown assets like old dev servers, misconfigured cloud storage, or abandoned domains. Cybercriminals constantly scan for forgotten assets, making it essential to find and fix vulnerabilities before they do.

A shadow IT policy is a set of rules that guide how employees use unauthorized technology, apps, or systems for work. It defines acceptable and unacceptable use of personal tools and unapproved software. The policy keeps company data secure and reduces risks from unauthorized tools. Shadow IT policies are important because if a data breach occurs due to an unapproved application, the policy demonstrates due diligence in attempting to prevent such incidents.