What Is Attack Surface Management?

Learn how to discover and secure every internet-facing asset before attackers find the vulnerabilities you don’t know exist.

Your company has more entry points than you realize. Every cloud service, remote access portal, and third-party integration creates another potential way in for attackers.

The problem is visibility. Most security teams can only protect assets they know about. But the average organization has 30% more external assets than their inventories show. Those unknown assets become prime targets.

Vulnerability exploitation now accounts for 20% of all initial breach access, up from 15% the previous year (Verizon’s 2025 Data Breach Investigations Report). Edge devices and VPNs make up 22% of those exploited vulnerabilities. Attackers are actively scanning for the assets you’ve forgotten about.

Attack surface management finds those blind spots before attackers do. Here’s how it works and why traditional vulnerability scanning isn’t enough.

Understanding Attack Surface Management

Security teams spend millions protecting their networks. But they can only protect what they know exists.

Your attack surface is everything an attacker could target. Every web application, API endpoint, cloud service, and remote access portal. Every subdomain, IP address, and third-party integration. Traditional security assumes you know where all these assets are. That assumption is wrong.

Attack vectors are different. They’re how attackers exploit those targets. Phishing, malware, and credential stuffing are vectors. The exposed VPN portal they target is part of your attack surface.

What Are the Three Types of Attack Surfaces?

Not all attack surfaces are digital. Attackers exploit whatever path offers the least resistance.

Digital Attack Surface

This is what most people think of when discussing attack surfaces. It includes all network connections, open ports, and running services. Every web application, API, database, and cloud resource. All the software vulnerabilities in your technology stack.

Your digital attack surface grows every time someone spins up a new cloud instance, adds a SaaS integration, or creates a test server they forget to decommission. Remote work expanded digital attack surfaces dramatically as companies rushed to enable VPN access and cloud collaboration.

Physical Attack Surface

Physical security still matters. This covers hardware devices, their components, and physical access to facilities where sensitive data lives. USB ports on workstations. Server rooms without proper access controls. Backup tapes stored in unlocked cabinets.

Physical attacks often combine with digital exploitation. An attacker who gains physical access to a network closet can plug in a rogue device. Someone who steals a laptop gets whatever credentials are cached on it.

Human Attack Surface

Your employees are attack vectors too. Social engineering, phishing campaigns, and manipulation tactics target the human element directly. Disgruntled employees with access to sensitive systems create insider threats.

The human attack surface is often the easiest to exploit. No technical vulnerability required. Just convince someone to click a link, share a password, or hold a door open.

Some security frameworks add a fourth category: operational attack surface. This covers vulnerabilities in business processes, like weak password policies, poor security training, or incident response plans that don’t work under pressure.

What Is an Example of an Attack Surface?

A typical mid-size company’s attack surface includes:

External-facing web assets: Marketing websites, customer portals, employee login pages, and API endpoints. Each one accepts input from the internet, which means each one can be probed for vulnerabilities.

Remote access infrastructure: VPN gateways, remote desktop services, and cloud-based access solutions. The 2025 DBIR found that edge devices and VPNs accounted for 22% of vulnerability exploitation incidents.

Cloud resources: Storage buckets, compute instances, databases, and serverless functions spread across multiple providers. Shadow IT often lives here, spun up by developers who needed something fast.

Email infrastructure: Mail servers, spam filters, and email security gateways. Email remains the top initial access vector for phishing attacks.

Third-party connections: Vendor integrations, partner APIs, and supply chain dependencies. Third-party involvement in breaches doubled to 30% according to Verizon’s 2025 DBIR.

The Equifax breach illustrates how a single overlooked asset destroys everything. Attackers exploited an unpatched Apache Struts vulnerability (CVE-2017-5638) on a web server that security teams had missed in their patching cycle. That one forgotten asset led to 147 million exposed records and $1.4 billion in costs.

Every company has assets like this. The question is whether you find them first or attackers do.

Why Does Attack Surface Management Matter?

Companies adopted cloud services, enabled remote work, and integrated third-party tools faster than security teams could track. The average organization has 30% more external assets than their inventories show.

Here’s what the data shows:

Vulnerability exploitation is rising fast. It now represents 20% of initial breach access, up from 15% the previous year (2025 DBIR). Attackers are actively scanning the internet for vulnerable assets, and automated tools make this trivially easy.

Remediation is failing. Only 54% of edge device vulnerabilities were fully remediated during the DBIR study period. The median time to remediate vulnerabilities is 32 days. That’s a month-long window where attackers can exploit known issues.

Unknown assets are prime targets. Research consistently shows that 76% of organizations have experienced attacks targeting unknown or unmanaged assets. You can’t patch what you can’t see.

The cost keeps climbing. Organizations using attack surface management tools reduced breach costs by $160,547 on average (IBM’s 2025 Cost of a Data Breach Report). The global average breach cost hit $4.88 million, the highest ever recorded.

ASM addresses this by providing continuous visibility into your actual attack surface, not just the assets you remember documenting. It finds the forgotten test server, the misconfigured S3 bucket, and the shadow IT application before attackers do.

But visibility alone isn’t enough. You need to understand what ASM tools actually do.

What Are the Main Functions of Attack Surface Management?

ASM isn’t a single tool. It’s a process with distinct phases that work together.

Asset Discovery

This is where ASM starts. Tools scan the internet for anything connected to your organization, including domains, subdomains, IP addresses, cloud resources, and third-party services. They use techniques like DNS enumeration, certificate transparency logs, and passive reconnaissance.

Good ASM discovery finds assets you never knew to scan. The subdomain someone registered for a conference five years ago. The cloud database a developer created for testing. The acquired company’s infrastructure that was never properly integrated.

Classification and Inventory

Once discovered, assets need categorization. What technology stack does each asset run? Who owns it? What data does it handle? Is it production or development?

Classification determines how you prioritize risks. A vulnerable test server with no real data is lower priority than a vulnerable customer portal processing transactions.

Vulnerability Assessment

With assets discovered and classified, ASM tools perform basic security checks from the outside: open ports, exposed services, SSL certificate issues, and cloud storage with public access. This gives you the attacker’s view. For deeper vulnerability assessment, you’ll still need traditional scanners, but now you know what to add to their scope.

Continuous Monitoring

Attack surfaces change constantly. New assets appear, configurations change, and new vulnerabilities emerge. ASM monitoring runs continuously to catch changes as they happen.

This is the key difference from point-in-time assessments. Your attack surface from last month isn’t your attack surface today.

How Does External Attack Surface Management (EASM) Work?

EASM is ASM focused on the attacker’s view. It specifically monitors internet-facing assets visible to anyone scanning from outside your network.

Where internal vulnerability management relies on agents and network access, EASM works without any access to your internal systems. It discovers assets the same way attackers do, through internet scanning, DNS lookups, and public data sources.

What EASM typically discovers:

• Subdomains you forgot existed
• Cloud resources with public exposure
• Expired or misconfigured SSL certificates
• Open ports running unnecessary services
• Development and staging environments accidentally exposed
• APIs without proper authentication
• Third-party services connected to your infrastructure

EASM tools also connect to threat intelligence sources. They check if your assets appear in breach databases, if your domains show up in phishing campaigns, or if your IP addresses are associated with malicious activity.

The output is a continuously updated inventory of your external attack surface that reflects real-world exploitability. Security teams can see exactly what attackers see, then fix exposures before exploitation happens.

How Do You Measure Attack Surface?

You can’t improve what you don’t measure. These metrics tell you if your ASM program is reducing risk.

Asset count and discovery rate: How many internet-facing assets do you have? More importantly, how many new assets does your ASM tool discover that weren’t in your existing inventory? High discovery rates indicate shadow IT problems.

Vulnerability density: Number of known vulnerabilities per asset, segmented by severity. Track this over time to see if you’re reducing exposure or accumulating technical debt.

Mean time to remediate (MTTR): How long does it take to fix discovered vulnerabilities? The 32-day median remediation time from the DBIR is a benchmark. You want to be faster, especially for critical issues.

Exposure window: How long are critical vulnerabilities exposed before remediation? This combines discovery time and remediation time to show total risk duration.

Third-party connection count: How many external services and vendors connect to your infrastructure? Each connection extends your attack surface and introduces supply chain risk.

Credential exposures detected: How many of your organization’s credentials appear in breached databases or dark web marketplaces? This metric connects ASM to credential-based attacks.

Attack surface growth rate: Is your attack surface expanding faster than you can secure it? Track new assets discovered monthly versus assets remediated or decommissioned.

The most actionable metric is remediation velocity. Finding vulnerabilities is meaningless though if they don’t get fixed before attackers exploit them.

What Challenges Do Security Teams Face with Attack Surface Management?

ASM sounds simple. It’s not.

Asset Sprawl and Shadow IT

Cloud computing made it trivially easy to create new infrastructure. Developers spin up resources without security review. Marketing teams launch microsites without IT involvement. Acquisitions bring entire unknown networks into your environment.

The result is asset sprawl that outpaces documentation. Every undocumented asset is a potential blind spot.

Multi-Cloud Complexity

Most organizations use multiple cloud providers plus on-premise infrastructure. Each environment has different security controls, different APIs, and different visibility tools. Correlating assets across AWS, Azure, GCP, and your data center requires integration work.

Many ASM tools excel in one environment but struggle with others. Comprehensive coverage often requires multiple tools or significant configuration effort.

Third-Party and Vendor Risks

Your attack surface extends into your vendors’ networks. When a supplier gets breached, attackers can pivot to your systems through established connections.

Third-party involvement in breaches doubled to 30% (2025 DBIR). But monitoring vendor security is difficult. You don’t control their infrastructure, and security assessments only provide point-in-time snapshots.

Alert Fatigue and False Positives

ASM tools generate alerts. Lots of alerts. Without proper tuning, teams drown in low-priority findings while missing the critical issues.

The solution is risk-based prioritization, but that requires understanding your business context. A generic ASM tool doesn’t know that your payment processing server matters more than your company blog.

Remediation Bottlenecks

Finding vulnerabilities is faster than fixing them. Security teams identify issues, but remediation requires coordination with application owners, change management processes, and testing. The 32-day median remediation time exists because organizations can’t move faster, not because they don’t want to.

How Can You Reduce Your Attack Surface?

Smaller attack surfaces mean fewer opportunities for attackers. Here’s how to shrink yours.

Maintain Continuous Asset Inventory

You can’t reduce what you can’t see. Deploy ASM tools that automatically discover and inventory all external assets. Decommission assets that no longer serve business purposes.

Make asset discovery part of your change management process. Before any new service goes live, it should be documented and included in your security monitoring scope.

Implement Network Segmentation

Flat networks let attackers move laterally after initial access. Segment your network so compromising one system doesn’t compromise everything.

Put critical assets in isolated segments with strict access controls. Use zero-trust principles where every access request requires authentication, regardless of network location.

Enforce Least Privilege Access

Every user and system should have minimum necessary permissions. Audit access rights regularly. Remove accounts that are no longer needed. Use privileged access management for administrative credentials.

This applies to service accounts and API keys too. Over-permissioned integrations extend your attack surface unnecessarily.

Patch Aggressively

The 32-day median remediation time is too slow for critical vulnerabilities. Establish SLAs based on severity. Critical vulnerabilities on internet-facing assets should be patched within days, not weeks.

Automate patching where possible. Use vulnerability management tools that integrate with your ASM platform to prioritize what gets patched first.

Monitor for Credential Exposure

Credentials are part of your attack surface too. When employee passwords appear in breached databases or dark web marketplaces, attackers can use them to access your systems, bypassing authentication entirely.

Implement credential monitoring that alerts when your organization’s passwords are exposed. Force password resets before attackers can use leaked credentials.

Remove Unnecessary Services

Every open port and running service is a potential target. Audit your external assets and disable services that aren’t required. Close unused ports. Remove default installations and test environments from production networks.

Less exposure means less to defend and less to go wrong.

But what about data attackers have already stolen?

How Does Attack Surface Management Connect to Dark Web Monitoring?

Traditional ASM focuses on what’s exposed. But attackers often have more information than just what they can scan.

Leaked credentials bypass authentication entirely. An attacker with valid credentials doesn’t need to exploit vulnerabilities. They just log in. Your attack surface includes every credential that’s been exposed in breaches, sold on criminal marketplaces, or stolen by infostealer malware.

Dark web markets sell access to your network. Initial access brokers sell entry points to already-compromised networks. Stolen credentials appear for sale. Ransomware gangs publish victim data on leak sites. Monitoring these sources catches threats traditional security tools miss.

Ransomware leak sites reveal supply chain compromises. When your vendor appears on a ransomware gang’s leak site, your data may be exposed too. Third-party risk monitoring extends your visibility into these supply chain threats.

Session tokens are more dangerous than passwords. Infostealer malware doesn’t just grab passwords. It captures session tokens that bypass MFA entirely. Monitoring for these exposures is essential because traditional credential resets don’t help.

The most effective approach combines ASM with dark web monitoring. Find your exposed assets AND the leaked credentials attackers could use to access them.

This combination provides complete visibility into both what attackers can see and what they already know.

Conclusion

Your attack surface is larger than you think. Shadow IT, forgotten servers, cloud misconfigurations, and third-party connections create blind spots that attackers actively exploit.

Attack surface management finds these blind spots before attackers do. It provides continuous visibility into your actual external footprint, not just the assets you remember documenting.

Key takeaways:

• Discovery is foundational. You can’t protect assets you don’t know exist. Most organizations find 30% more external assets than documented.
• Vulnerability exploitation is accelerating. 20% of breaches start with exploited vulnerabilities. The median 32-day remediation time gives attackers a wide window.
• Third-party risk is expanding. Supply chain involvement in breaches doubled to 30%. Your attack surface extends into your vendors’ networks.
• Credentials are part of your attack surface. Leaked passwords and session tokens let attackers bypass authentication entirely.

Start by mapping your external attack surface with ASM tools. Prioritize remediation based on real risk, not just severity scores. Monitor for credential exposures that could give attackers a way in.

The organizations that find their blind spots first are the ones that avoid becoming breach statistics.

Ready to see what attackers can see about your organization? Check your dark web exposure to find leaked credentials, or book a demo to see how Breachsense provides complete external threat visibility.