External Attack Surface Management

EASM gives you three key benefits. First, it finds unknown assets across your organization - subdomains, APIs, and shadow IT that traditional asset management misses. Second, it identifies security issues in public-facing assets before attackers exploit them. Third, it helps you prioritize which vulnerabilities pose the greatest threat based on exposure and potential impact. External attack surface management becomes essential as you expand your 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.

Your external attack surface is all digital assets and services you operate 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. Your external attack surface grows as you 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 external attack surface. These tools continuously scan the internet to find assets associated with your organization - domains, subdomains, cloud services, and exposed ports you might not know about. They check for vulnerabilities, misconfigurations, expired certificates, and other security issues. EASM tools show you your external footprint in real time 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.

You can’t protect what you don’t know exists. With cloud services and remote work, you’re creating new digital assets faster than ever and 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. You become vulnerable to attacks through unknown assets like old dev servers, misconfigured cloud storage, or abandoned domains. Attackers constantly scan for forgotten assets, so you need 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.