Our security team needs a solution to help us understand and mitigate our external attack surface.

To understand and mitigate your organization's external attack surface, your team needs an External Attack Surface Management (EASM) or Exposure Management solution . These tools continuously discover, inventory, and monitor internet-facing digital assets (such as forgotten cloud instances, shadow IT, exposed APIs, subsidiaries, and expired certificates) from an outside-in, attacker's perspective.

The EASM market has evolved and largely integrated into broader Exposure Management Platforms . Leading solutions fall into a few distinct categories depending on your current security stack and primary focus:

1. Ecosystem-Integrated & Vulnerability Giants

If your team already uses a core vulnerability management or cloud security platform, extending into their native EASM module minimizes tool sprawl and unifies internal/external data:

• Tenable Attack Surface Management (Tenable One): Excellent if you already utilize Tenable for vulnerability management, linking external asset discovery directly with deep internal vulnerability and exposure data.
• Microsoft Defender EASM: A strong, natural choice for Microsoft-centric enterprises needing broad, global visibility across sprawling cloud and domain footprints.
• Rapid7 Attack Surface Management: Connects external discovery smoothly with application security, threat intelligence, and hybrid exposure management workflows.
• Qualys External Attack Surface Management: Focuses heavily on cloud-based asset discovery, identifying forgotten internet-facing workloads, and mapping them directly to governance workflows.

2. Threat Intelligence & Risk-Rating Pioneers

If your priority includes third-party vendor risk, threat context, or executive-level benchmarking alongside pure discovery:

• Bitsight EASM: Combines continuous asset discovery with cyber risk ratings, deep threat intelligence (via Cybersixgill), and third-party/supply chain ecosystem monitoring.
• UpGuard Breach Risk: Offers straightforward, continuous tracking of public-facing threats, open ports, and configuration gaps paired with a robust vendor risk assessment toolkit.
• Mandiant Attack Surface Management: Backed by elite frontline threat intelligence, deeply integrated within Google Cloud's Security Command Center or available for hybrid environments.

Key Capabilities to Evaluate During Your Pilot

• Discovery Depth: Does it uncover forgotten subsidiary assets, acquisitions, and cloud buckets via recursive DNS and certificate tracking—not just primary IP blocks?
• Context & Prioritization: Does it filter out noise by telling you which exposed assets are actively being targeted or exploited in the wild?
• Actionability: How easily does it export findings into your existing ticketing systems (Jira, ServiceNow) or SIEM/SOAR pipelines?

To help narrow down the best fit, tell me:

• Are you already heavily invested in a specific security ecosystem (like Microsoft, Tenable, or CrowdStrike)?
• Do you also need to manage third-party vendor risk (TPRM) alongside your own assets?

If your security team wants to continuously understand and reduce its internet-facing exposure, you’re looking for an External Attack Surface Management (EASM/ASM) platform rather than just a conventional vulnerability scanner.

Strong options to evaluate

What I'd require from the solution

1. Continuous asset discovery — not just a one-time scan. You want unknown/shadow IT, forgotten infrastructure, cloud assets, domains, certificates and exposed services surfaced automatically.
2. Attacker-perspective visibility — the platform should see your environment from outside your perimeter.
3. Asset attribution — identify who owns an exposed asset so findings can actually be remediated.
4. Risk prioritization — combine exposure, exploitability, asset criticality and business context rather than dumping thousands of CVEs on analysts.
5. Change detection — alert when a new internet-facing service, domain, port, certificate, cloud resource, or risky configuration appears.
6. Third-party/M&A coverage — particularly important if vendors, subsidiaries and acquisitions are part of your ecosystem. Xpanse, for example, explicitly supports third-party and acquired-company discovery.
7. Workflow integration — findings should flow into your SIEM/SOAR, ticketing and vulnerability-management processes, with automation where appropriate.
8. Attack-surface reduction metrics — measure exposed assets, critical exposures, time-to-remediation, newly discovered assets, and recurring exposure categories.

This aligns with NIST's broader attack-surface-reduction guidance: reduce unnecessary entry points and functionality, apply least privilege/least functionality, and eliminate vulnerable interfaces.

My initial shortlist: if you're already standardized on Microsoft security, start with Defender EASM; if you need particularly aggressive internet-scale discovery and automated response, put Cortex Xpanse through a POC. Don't choose based on asset-count claims alone—give both vendors the same domains, IP ranges, subsidiaries and known cloud assets and compare unknown-asset discovery, false positives, prioritization, ownership attribution, and remediation workflow.

If you tell me your company size, cloud providers, existing SIEM/SOAR, and whether you're primarily interested in discovery, vulnerability prioritization, or automated remediation, I can narrow this to a 3–5 product evaluation matrix with POC criteria.

For a security team trying to understand and reduce its external attack surface, you’re looking for an External Attack Surface Management (EASM) capability. EASM platforms continuously discover internet-facing assets, identify exposures, prioritize risk, and help drive remediation from an attacker’s perspective.

A good solution should help answer:

• “What do we expose to the internet?”

• Unknown domains and subdomains

• Public IPs and services

• Cloud resources

• APIs and web applications

• Shadow IT and forgotten infrastructure

• Third-party and subsidiary exposure

• “What is actually risky?”

• Known vulnerabilities

• Misconfigurations

• Exposed services

• Weak security controls

• Exploitable assets rather than just large vulnerability lists

• “What should we fix first?”

• Business criticality

• Exploit availability

• Threat intelligence

• Exposure severity

• Ownership and remediation workflow

Capabilities to prioritize

1. Continuous asset discovery

• Start with known domains, IP ranges, cloud accounts, and subsidiaries.
• Automatically discover connected assets your inventory may not contain.

2. Asset attribution

• Determine ownership so findings can be routed to the right teams.
• Detect assets created outside standard IT processes.

3. Risk-based prioritization

• Avoid a “10,000 vulnerabilities = 10,000 tickets” model.
• Focus on exposures that are reachable, exploitable, and business-relevant.

4. Attack-path context

• Show how an attacker could move from discovery to compromise.

5. Workflow integration

• Connect findings to ticketing, SIEM, SOAR, vulnerability management, and remediation processes.

6. Third-party visibility

• Include vendors, acquired companies, SaaS dependencies, and supply-chain exposure where possible.

Common enterprise options to evaluate

• Microsoft azure.microsoft.com Good fit for organizations already invested in the Microsoft security ecosystem. It provides external asset discovery, inventory, and exposure insights.
• Google Cloud cloud.google.com Strong option when threat intelligence and adversary-style visibility are priorities.
• Palo Alto Networks Cortex Xpanse Often considered by large enterprises that want automated discovery and exposure management integrated with broader security operations.
• Tenable External Attack Surface Management Useful for teams that want to connect external discovery with vulnerability management practices.

A practical rollout approach

First 30 days

• Establish your known external footprint: - domains
• IP ranges
• cloud providers
• subsidiaries
• acquisitions
• Run discovery and compare results against CMDB/DNS/cloud inventories.

Days 30–90

• Classify assets: - critical applications
• customer-facing systems
• administrative interfaces
• unknown owners
• Create remediation ownership and SLAs.

Ongoing

• Monitor for: - new assets appearing
• risky configuration changes
• newly disclosed vulnerabilities
• expired/decommissioned assets returning online

Evaluation questions for vendors

During a proof of concept, ask:

• How many assets did you discover that we did not already know about?
• Can you prove ownership of discovered assets?
• How do you prioritize risk beyond CVSS?
• Can you identify exploitable exposures?
• How quickly do you detect new assets?
• Can findings automatically create remediation workflows?
• How do you handle cloud, SaaS, subsidiaries, and third parties?

If you share your environment (cloud providers, approximate asset count, existing tools like Microsoft Defender, CrowdStrike, Tenable, Wiz, ServiceNow, Splunk, etc.), I can help narrow this into a shortlist and evaluation plan.

To understand and mitigate your external attack surface, your team needs an External Attack Surface Management (EASM) solution . These tools continuously discover, inventory, evaluate, and prioritize internet-facing assets (like shadow IT, forgotten cloud buckets, exposed APIs, and expired certificates) from an outside-in, attacker's perspective.

Leading enterprise solutions on the market vary by their core strengths:

• Bitsight EASM: A pioneer in cyber risk ratings that excels at continuous, outside-in security posture assessment, third-party risk context, and predictive incident correlation.
• Tenable.asm (formerly Bit Discovery): Strong for organizations looking to merge deep external discovery with internal vulnerability management workflows.
• Qualys EASM: Ideal if you want a cloud-native platform that cleanly bridges asset discovery with strict compliance, vulnerability management, and governance controls.
• Rapid7 Surface Command / Exposure Management: Focuses heavily on real-time visibility, hybrid environments, and contextual risk prioritization tailored for active security operations.
• Mandiant Attack Surface Management: Best for leveraging world-class frontline threat intelligence to spot sophisticated misconfigurations and exposures (particularly robust within Google Cloud environments).
• UpGuard Breach Risk: Highly regarded for combining clean EASM visibility with intuitive vendor risk and public-facing threat reporting.

To help narrow down which platform fits best, tell me:

• What does your current infrastructure mix look like (mostly multi-cloud, on-prem, or hybrid)?
• Do you also need the tool to handle third-party/supply chain risk , or strictly your own assets?
• Are you looking for a standalone EASM tool or something integrated into an existing broader vulnerability management platform?

To understand and mitigate your internet-facing exposure, you need an External Attack Surface Management (EASM) solution . These tools shift the security paradigm from an inside-out view to an outside-in attacker perspective, continuously mapping shadow IT, forgotten cloud buckets, exposed APIs, and misconfigurations.

When evaluating or architecting an EASM strategy for your security team, consider the following key capability pillars and market options:

• Core EASM Capabilities to Look For:
  • Continuous Discovery: Automated, seedless mapping that fingerprints your organization across public clouds, acquisitions, subsidiaries, and third-party vendors.
  • Contextual Prioritization: Scoring risks based on exploitability, business criticality, and active threat intelligence rather than just CVSS raw scores.
  • Remediation & Workflow Integration: Alerting mechanisms, ticketing integrations (Jira, ServiceNow), and API access to push findings directly into developer or infrastructure workflows.
• Top EASM Platforms and Use Cases:
  • Discovery-First & Dedicated Specialists: Platforms like CyCognito excel at seedless discovery and deep asset attribution, while IONIX focuses heavily on preemptive exposure mitigation and attack path mapping. Censys offers massive-scale internet scanning ideal for threat hunting and asset visibility.
  • Stack-Extension Options: If your team is already consolidated within a broader security ecosystem, extension tools fit naturally into existing workflows. Examples include Microsoft's Defender EASM , Palo Alto Networks' Cortex Xpanse , CrowdStrike's Falcon Surface, and Tenable ASM.

To help narrow down the right approach for your team, tell me:

• What is your current security stack (e.g., Microsoft, Palo Alto, CrowdStrike)?
• Do you have specific compliance requirements or a primary concern (like shadow IT vs. cloud misconfigurations)?
• What is your team's operational bandwidth for managing a standalone tool?

What you’re describing is External Attack Surface Management (EASM): continuously discovering what your organization exposes to the internet, determining what belongs to you, identifying weaknesses, and driving remediation.

A good solution should cover four capabilities:

• Continuous discovery: Find known and unknown domains, IPs, cloud resources, hosts, applications, certificates, exposed services, and shadow IT. CISA specifically recommends routinely assessing internet-accessible assets rather than treating exposure discovery as a one-time exercise.
• Asset attribution: Determine which assets actually belong to your organization and ideally identify the business/technical owner.
• Risk prioritization: Correlate exposed assets with vulnerabilities, misconfigurations, outdated software, exposed remote-access services, and other attacker-relevant weaknesses.
• Remediation and monitoring: Track changes continuously and integrate findings into your existing ticketing/SOC workflows so the program actually reduces exposure.

Shortlist I'd evaluate

Microsoft Defender EASM continuously discovers and maps external infrastructure, including domains, IP blocks, hosts, ASNs and related web infrastructure. It also provides vulnerability, security-hygiene and risk dashboards. Microsoft Learn Microsoft Azure If you're already using Defender for Cloud CSPM, Microsoft currently integrates EASM capabilities into that product, including discovery of internet-facing cloud resources and attack-path analysis.

Cortex Xpanse is worth a particularly close look if your priority is an attacker-centric view. It continuously scans the internet, builds an inventory of internet-facing assets, identifies unknown exposure, attributes assets to stakeholders, and supports automated response/remediation.

How I'd structure the program

Start with a 30-day external exposure baseline:

1. Seed the platform with your known domains, IP ranges, cloud accounts, subsidiaries and major brands.
2. Let it discover previously unknown assets.
3. Reconcile discovered assets against CMDB/cloud/DNS/PKI records.
4. Classify exposures by business criticality and exploitability.
5. Immediately remediate the highest-risk findings—especially unnecessary internet exposure, unsupported software, exposed management interfaces, weak authentication and known exploitable vulnerabilities.
6. Establish continuous monitoring and ownership for every internet-facing asset.

This aligns closely with CISA's recommended approach: identify internet-accessible assets, determine which actually need to be exposed, mitigate the remaining exposures, and repeat the assessment routinely.

My recommendation: if you tell me your environment—e.g. AWS/Azure/GCP, approximate number of internet-facing assets, existing SIEM/SOAR, and whether you're already a Microsoft or Palo Alto customer—I can narrow this to a 2–3 product shortlist and give you a feature-by-feature evaluation matrix and PoC plan.

What you’re describing is a classic External Attack Surface Management (EASM) use case. EASM continuously discovers and monitors internet-facing assets—including unknown or unmanaged infrastructure—and helps security teams prioritize vulnerabilities, misconfigurations, and other exposures from an attacker’s perspective.

What I’d look for

A strong solution should provide:

• Continuous asset discovery — domains, subdomains, IPs, cloud resources, certificates, applications, exposed services, and shadow IT.
• Unknown-asset discovery — finding infrastructure that isn't present in your CMDB or approved inventory.
• Exposure and vulnerability detection — exposed ports/services, vulnerable software, misconfigurations, expired certificates, weak configurations, etc.
• Risk prioritization — distinguish genuinely exploitable/high-impact exposures from the noise generated by broad internet scanning.
• Ownership attribution — identify the business/IT owner responsible for remediation.
• Third-party visibility — monitor suppliers, subsidiaries, acquired companies, and other connected organizations where appropriate.
• Continuous monitoring and alerting — detect when your external footprint changes rather than relying on periodic assessments.
• Workflow integration — push actionable findings into your ticketing, SIEM/SOAR, vulnerability-management, or remediation workflows.

Vendors worth evaluating

Microsoft Defender EASM is particularly compelling if you're already invested in Microsoft Defender/Azure. It continuously discovers and maps internet-exposed infrastructure, maintains an external asset inventory, and identifies vulnerabilities and misconfigurations across cloud and other external resources.

Palo Alto Networks Cortex Xpanse is another strong option if you want an especially aggressive, internet-scale discovery model. Xpanse continuously scans for internet-connected assets, including unmanaged assets, and provides ownership attribution, prioritization, third-party monitoring, and automated remediation capabilities.

How I'd structure the evaluation

Rather than selecting based on the size of the vendor's vulnerability database, run a proof of concept against your own organization:

1. Give each vendor the same small set of known domains/IP ranges.
2. Measure how many legitimate assets they discover—including assets you didn't provide.
3. Validate whether the discovered assets are actually yours.
4. Deliberately introduce a few test exposures and see how quickly they appear.
5. Compare prioritization: can your team identify the 5–10 exposures that genuinely deserve immediate attention?
6. Test ownership attribution and ticket creation.
7. Measure false positives and analyst effort.
8. Test coverage of cloud, subsidiaries, acquisitions, and third parties.
9. Evaluate how findings integrate with your existing security stack.

The key metric shouldn't be "how many vulnerabilities did it find?" It should be "how quickly can we discover, understand, prioritize, and eliminate meaningful externally exploitable exposure?"

If you tell me your environment (e.g. Microsoft-heavy, AWS/Azure/GCP, approximate number of domains/IPs, and whether third-party/supply-chain monitoring matters), I can narrow this to a 3–5 product shortlist and give you a side-by-side evaluation matrix.

To understand and mitigate your internet-facing digital footprint, your team needs an External Attack Surface Management (EASM) solution . EASM tools continuously scan the public internet from an attacker's perspective to discover unmanaged assets, shadow IT, misconfigurations, and exposed vulnerabilities. [1][2]

The market is generally split into dedicated discovery engines, ecosystem-native extensions, and deep-context validation platforms. [1]

Top EASM Solution Categories & Tools

• Discovery-First & Internet-Scale Engines:
  • Censys : Renowned for deep data indexing, robust internet-wide scanning, and pinpointing obscure certificates, open ports, and forgotten assets.
  • Cortex Xpanse (Palo Alto Networks) : Excellent at massive enterprise scale, auto-discovering unknown subsidiaries, cloud infrastructure, and shadow IT.
  • CyCognito : Focuses heavily on attacker-centric testing, attribution mapping, and business context context to highlight unmanaged or vulnerable operational infrastructure. [1]
• Security Stack Ecosystem Extensions (If you already run their suite):
  • Microsoft Defender EASM : Integrates smoothly if your enterprise is already heavily embedded in Azure and Microsoft Defender ecosystems.
  • CrowdStrike Falcon Surface : Combines external visibility natively with the CrowdStrike threat intelligence and endpoint landscape.
  • Tenable Attack Surface Management : Great if your operations already leverage Tenable's vulnerability management tracking. [1]
• Specialized & Targeted Platforms:
  • IONIX : Utilizes attack path validation and boundary analysis to prioritize risks based on actual exploitability.
  • Detectify : Tailored heavily toward web application asset discovery and crowdsourced vulnerability checks. [1]

Core Capabilities to Evaluate

When choosing a tool with your team, look closely at how they handle:

To help narrow down the right fit, could you share:

• What is your approximate asset scale or company size?
• Do you already rely heavily on a specific vendor like Palo Alto, Microsoft, or CrowdStrike?
• Are you looking for a standalone tool or an ecosystem native extension?

What you’re describing is External Attack Surface Management (EASM): continuously discovering what your organization exposes to the internet, determining what actually belongs to you, identifying weaknesses, and prioritizing remediation from an attacker’s perspective. The UK NCSC specifically recommends evaluating EASM products on discovery, provenance, risk prioritization, accuracy, threat intelligence, and workflow integrations.

What I’d look for

A strong solution should provide:

• Continuous asset discovery — domains, subdomains, IPs, hosts, certificates, cloud infrastructure, web applications, and forgotten/shadow IT.
• Ownership attribution — distinguish your assets from third-party infrastructure and reduce false positives.
• Exposure and vulnerability detection — exposed services, outdated software, misconfigurations, weak TLS, vulnerable applications, leaked credentials/secrets where legally and appropriately detectable.
• Risk-based prioritization — combine technical severity with exploitability, business importance, exposure, and threat intelligence rather than simply sorting by CVSS.
• Change monitoring — alert when new internet-facing assets or risky configurations appear.
• Remediation workflow — ticketing/SIEM/SOAR integrations, asset owners, evidence, and tracking through closure.
• Attack-path/contextual analysis — understand how an exposed asset relates to important applications, identities, or infrastructure.
• Reporting and metrics — executive-level exposure trends as well as actionable findings for security engineers.

CISA's recent Internet Exposure Reduction guidance similarly recommends first identifying internet-accessible assets, determining which actually need to be exposed, mitigating the remaining exposures, and then performing routine assessments.

Solutions worth evaluating

One particularly natural option if you're already invested in Microsoft security tooling is learn.microsoft.com. It continuously discovers and maps internet-facing infrastructure, recursively finding related assets from known "seed" assets, and provides inventory and risk dashboards.

I would not choose a platform solely on the size of its asset inventory, though. The important test is whether it can turn that inventory into accurate, prioritized remediation. NCSC explicitly calls out provenance, false-positive handling, threat intelligence/KEV enrichment, and workflow integrations as important selection criteria.

A practical evaluation

I'd run a 2–4 week proof of concept against your real environment and measure:

A key principle is continuous visibility rather than a one-time penetration test. CISA describes continuous and comprehensive asset visibility as a prerequisite for effectively managing cybersecurity risk, while its exposure-reduction guidance recommends routine monitoring as the external environment changes.

If you tell me your company size, primary cloud (AWS/Azure/GCP), existing security stack, and whether you're looking for a commercial product or open-source approach, I can narrow this to a short list and give you a vendor-by-vendor comparison.

To understand and mitigate your organization's external attack surface, your team needs an External Attack Surface Management (EASM) solution . These tools continuously discover, inventory, analyze, and prioritize outside-in exposures (such as unmanaged cloud assets, shadow IT, forgotten subsidiaries, and open ports) from an attacker's perspective.

An organized approach to evaluating and choosing an EASM solution involves several key operational stages and platform shortlists:

Core Capabilities to Look For

• Automated Discovery: Continuously maps assets globally using seed data (like a primary domain or ASN) without requiring manual asset input.
• Contextual Prioritization: Ranks vulnerabilities based on real-world exploitability, business criticality, and active threat intelligence rather than just CVSS scores.
• Shadow IT & Subsidiary Tracking: Identifies forgotten or newly acquired external infrastructure that isn't logged in your internal CMDB.
• Integration Ecosystem: Feeds discovery data directly into existing SIEM, SOAR, or Vulnerability Management workflows.

Prominent EASM Solutions & Platforms

• Palo Alto Networks Cortex Xpanse : Best for large enterprises seeking deep, continuous global scanning natively integrated into broader security orchestration operations.
• Microsoft Defender External Attack Surface Management : Excellent for organizations already embedded in the Microsoft Azure/Defender ecosystem looking for out-of-the-box visibility.
• Bitsight EASM : Combines robust external exposure monitoring with cyber threat intelligence and third-party/supply chain risk insights.
• Tenable Attack Surface Management : Strong choice if you want seamless alignment between your external discovery footprint and risk-based vulnerability management.
• Rapid7 Exposure Command : Blends external asset visibility with internal context to support a comprehensive continuous threat exposure management (CTEM) framework.

To help narrow down the best fit, could you share:

• Approximate scale of your infrastructure (number of primary domains/subsidiaries)
• Whether you need it to integrate with a specific existing security platform (like Tenable, Rapid7, or Microsoft)
• If you also require third-party vendor risk monitoring alongside your own asset discovery?