As organizations adopt cloud services, remote work, third-party integrations, and digital transformation initiatives, their IT environments have become increasingly complex—and increasingly visible to attackers. Every exposed web server, misconfigured cloud bucket, forgotten subdomain, or unsecured API becomes a doorway that adversaries can exploit. A 2021 report revealed that 69% of organizations had experienced at least one cyberattack initiated through an unknown or unmanaged internet-facing asset.

This growing attack surface poses a significant challenge for security teams. It’s no longer enough to defend what’s inside the perimeter; today, visibility and control must extend to every asset connected to the internet, whether it’s actively in use or quietly forgotten. That’s where Attack Surface Management (ASM) comes in.

In this article, we’ll explore what Attack Surface Management is, how it works, and why it’s become a critical component of modern security strategies.

What is an attack surface?

An attack surface refers to the full range of points where an unauthorized user could attempt to enter or extract data from your systems. This includes every part of your IT environment that could be exploited, whether it’s visible on the internet or operating inside your internal network. From employee laptops and internal databases to cloud platforms, APIs, mobile apps, and even physical devices, any component that processes or stores data is a potential doorway for attackers.

What is an external attack surface?

An external attack surface specifically refers to all publicly accessible entry points an attacker could use to gain unauthorized access to your systems or data. It includes everything from public-facing websites and APIs to cloud services, third-party tools, and even forgotten or legacy infrastructure that’s still accessible online. In short, if it’s connected to the internet and belongs to your organization, it’s part of your external attack surface.

The number of internet-facing assets an organization has can proliferate very quickly, creating a problem for security teams. Many of these assets are created outside of central IT oversight, making them easy to overlook, and attractive targets for attackers.

This is why Attack Surface Management—particularly External Attack Surface Management—has become so critical. By continuously discovering and monitoring your external assets, you can reduce your risk and respond faster to emerging threats before an attacker finds their way in.

What is Attack Surface Management (ASM)?

ASM is the ongoing process of identifying, monitoring, and reducing all the assets that could be targeted in a cyberattack. Its goal is to give organizations complete visibility into their digital footprint—both internal and external—so they can proactively manage and minimize risk.

Organizations turn to ASM for a variety of critical reasons:

• Detect unknown and unmanaged assets: Identify shadow IT, hidden projects, and overlooked infrastructure across on-premise and cloud environments.
• Expose weak points missed by traditional tools: Go beyond the most common vulnerabilities to uncover subtle or emerging risks.
• Reduce internet-facing exposure: Eliminate unnecessary online assets; if it’s not online, it can’t be attacked.
• Assess third-party and vendor risk: Evaluate the digital risk posture of suppliers, partners, and external services.
• Detect external threats: Monitor for risks like leaked credentials, domain spoofing, and brand abuse happening outside your infrastructure.
• Automate manual processes: Save time by replacing fragmented open-source scanning efforts with automated, centralized discovery and analysis.
• Enable cross-team collaboration: Provide a unified security view across departments, allowing different teams to track assets, share insights, and align on priorities.
• Deliver executive-level visibility: Offer clear reporting and metrics so leadership can easily track security posture and progress over time.

What is External Attack Surface Management (EASM)?

EASM is a part of ASM that focuses specifically on identifying and managing all internet-facing assets that belong to an organization. External assets are often the first things attackers scan for, and any weak spot could be an open door. That’s why EASM is critical for identifying unknown risks before adversaries do, and reducing the attack surface they can exploit.

Key benefits of EASM include:

• Discovering shadow assets deployed outside of IT’s visibility
• Detecting misconfigurations and exposure caused by human error
• Reducing external footprint to limit what’s publicly accessible
• Monitoring for threat activity such as cybersquatting, phishing domains, or exposed credentials
• Improving incident response by maintaining an up-to-date inventory of what’s online

In short, EASM solutions gives you the attacker’s perspective of your organization’s online presence. By regularly scanning and assessing your external assets, it helps reduce the likelihood of breaches and gives security teams the intelligence they need to take fast, effective action.

Why Attack Surface Management is important

As organizations push forward with digital transformation, adopt cloud infrastructure, and enable remote work, the number of exposed IT assets increases dramatically. Many of these assets are created quickly, deployed outside of IT’s direct control, or forgotten altogether, making them difficult to track and secure.

Several key trends are contributing to this challenge:

• Rapid digitization across industries to stay competitive
• Widespread cloud adoption and fast-paced cloud deployments
• Multi-cloud strategies that spread infrastructure across providers
• SaaS and low-code tools that allow non-IT staff to deploy applications 
• A mobile, flexible workforce connecting from anywhere, on any device
• Shortage of skilled cybersecurity professionals and limited resources
• Constant asset turnover that outpaces traditional vulnerability scanning cycles

Because of all these factors, ASM has becomes an essential part of cybersecurity strategies. ASM provides an automated, continuous way to detect and monitor all exposed assets—across clouds, departments, and geographies. It eliminates the guesswork, speeds up discovery, and ensures that security teams always have a clear view of what’s online and at risk.

What’s the difference between Attack Surface Management and vulnerability scanning? 

While ASM and vulnerability scanning are both important components of a security strategy, they serve different purposes and operate in fundamentally different ways.

Vulnerability scanners are designed to inspect known assets for known software flaws. They work from a predefined list of IP addresses or systems and check for missing patches, misconfigurations, or outdated software. In contrast, ASM solutions focus on the discovery and monitoring of all internet-exposed assets, especially those that may be unknown or unmanaged.

Here are a few key ways ASM differs from traditional vulnerability scanning:

• Discovery of unknown assets:  Vulnerability scanners typically require a list of known IPs or hosts to begin scanning. ASM, on the other hand, starts with minimal input (often just a domain name) and uses DNS-based discovery methods to uncover both known and previously unknown assets, such as forgotten subdomains or unmonitored cloud instances.
• Broader risk detection: While vulnerability scanners concentrate on identifying software vulnerabilities, ASM identifies a wider range of risks such as exposed APIs, misconfigured services, open ports, and leaked credentials. It focuses on what an attacker can see and access from the outside.
• Non-intrusive by design: Vulnerability scans can be aggressive and may inadvertently disrupt systems, especially if misconfigured. ASM solutions, by contrast, simulate normal internet traffic and are non-invasive, making them safer to run continuously without risking operational impact.

In summary, ASM helps you understand what’s exposed, while vulnerability scanning helps you understand what’s vulnerable—but only within the scope of what you already know. Together, they can provide a more complete picture of your security posture.

Key features of an ASM platform  

ASM empowers cybersecurity professionals by reducing much of the heavy manual labor so they can focus on actually solving the issues instead of finding them. Technically skilled professionals know how to use the broad set of available open source scanning tools and security testing scripts, but correlating and storing all the returned data and conclusions is not an easy thing to do. 

An ASM platform is heavily automated and should be easy to set up and get started. 

An ASM solution typically has three core key features: 

• Continuous discovery 
• Automated security analysis 
• Risk-based follow-up

Three key features of an ASM solution 

1. Continuous discovery 

The core purpose of an ASM solution is to automate the discovery of your assets. Ideally, it should require nothing more than your primary domain (e.g. mycompany.com) to begin mapping your external footprint. For larger organizations, a list of primary domains can be used to provide broader coverage, with no need to supply IP addresses upfront.

That said, the option to manually add IP ranges should still be available for special cases where automated discovery methods might fall short. A robust ASM platform uses intelligent search algorithms to identify assets with high accuracy and minimal false positives, building a comprehensive view of your internet-facing environment.

The discovery process is continuous and each scan will find assets that will trigger new scans. Because of this ongoing process, any newly deployed or decommissioned assets are detected and reported regularly—typically on a weekly basis—giving your security team near real-time visibility into changes in your attack surface.

Typical asset elements that will be discovered include: 

• All DNS records 
• All related IP addresses 
• WHOIS or DNS registration info 
• Geo locations of the asset 
• Hosting providers in charge of the asset 
• All open ports 
• All used SSL/TLS certificates and their details 
• Email systems 
• DNS systems 
• Applications like: websites, emails, DB’s, remote access, fileshares, etc. 
• Software versions used across discovered assets and applications 
• Login pages 

2. Automated and continuous security analysis 

Once assets are discovered, the next step is to analyze and verify them for potential security issues. This involves assessing exposed systems to identify misconfigurations, vulnerabilities, and other weaknesses that could be exploited.

As outlined by SANS Security Awareness, the Cyber Kill Chain model describes the typical stages of a cyberattack, starting with reconnaissance, the phase where attackers gather information about their target. Modern threat actors operate like professional businesses, using advanced tooling, automation, and large-scale infrastructure to scan and map organizations rapidly and at scale.

Potential security issues include:

• Software vulnerabilities: Based on version information, outdated or unpatched software can expose known security flaws.
• Insecure email configurations: Missing or incorrect SPF, DMARC, or DKIM records can leave your domain vulnerable to spoofing and phishing.
• Weak encryption protocols: The use of outdated SSL/TLS versions (e.g. SSLv2.0, SSLv3.0, TLSv1.0) puts data at risk during transmission.
• Unsecured DNS setups: DNS configurations lacking DNSSEC support are more susceptible to spoofing and redirection attacks.
• Default installations: Default web server pages can signal an unfinished or unconfigured deployment, which may attract attackers.
• Misleading error codes: HTTP errors or misconfigured responses can indicate obsolete or improperly maintained websites.
• Unencrypted login pages: Login forms served over HTTP or unsecured FTP expose credentials to interception.
• Unnecessary exposed services: Open access to services like databases, Telnet, RDP, or VNC can provide attackers with easy entry points.
• Stolen credentials: Leaked usernames and passwords found in data breaches or on the dark web can lead to unauthorized access.
• Phishing and cybersquatting sites: Lookalike domains or fraudulent websites designed to impersonate your brand and deceive users.

3. Risk-based prioritization

An ASM solution will prioritize the identified issues out of the box with a built-in risk-based engine. This is an excellent first start for any organization. 

The first and most critical step is to address the highest-risk issues across your entire environment, regardless of how critical the underlying system may seem. Attackers often target less prominent or lightly monitored systems as an easy entry point, then move laterally through the network to reach high-value assets. This tactic is common in ransomware attacks, where compromising a single weak system or user can lead to widespread impact.

It’s important to remember that not all assets carry the same business value. Once major vulnerabilities are addressed across the board, organizations can begin to fine-tune their response strategy by tagging and categorizing assets based on business priority, sensitivity, or ownership.

An ASM solution will typically give a risk score and a trend line over time so management can follow up on the evolution of the work done and the remaining risk. 

Try Outpost24’s EASM solution for free 

Outpost24’s External Attack Surface Management (EASM) platform gives you full visibility into your internet-facing assets—both known and unknown—and continuously monitors for vulnerabilities, misconfigurations, and other high-risk exposures.

With powerful discovery capabilities and built-in threat intelligence, our platform helps organizations not only identify and prioritize security issues, but also take action to remediate them, strengthening your overall cyber resilience.

Book your free attack surface analysis today and see how Outpost24 can help you stay ahead of threats before they become breaches.