Every attack surface management (ASM) tool on the market in 2026 can find your internet-facing assets. Discovery stopped being the differentiator two or three years ago. What separates the tools now is what happens after discovery: whether an exposure is validated or merely scored, how fast you hear about a change, what the product does with leaked credentials, how it integrates with the testing you already run, and, for a growing number of buyers, where the resulting inventory of your weak points physically lives.
This guide covers the tools most security teams shortlist for external attack surface management (EASM), how to evaluate them, and where each one fits. It includes our own product, and it says plainly where we are not the right choice.
What an ASM tool has to do in 2026
Before comparing vendors, it helps to separate the capabilities, because most marketing pages blur them together:
- Discovery. Enumerate domains, subdomains, hosts, IPs, open ports, services, and certificates from a seed scope. Good tools combine passive sources (certificate transparency logs, DNS datasets, historical archives) with active techniques (subdomain brute-forcing, port and web-port probing) so they find the forgotten staging host, not only the assets in your CMDB.
- Exposure detection. Attach findings to each asset: expiring or weak TLS, exposed admin interfaces, risky services, DNS hygiene problems, missing email-security records (SPF, DMARC, DKIM, MTA-STS), and technology fingerprints.
- Breach and credential intelligence. Correlate breach corpora against the domains and email addresses in scope, so leaked employee credentials surface next to the systems they can unlock.
- Risk scoring and prioritization. Score each exposure and roll the scores up to an organization view, so the team works the worst thing first rather than the newest thing.
- Continuous monitoring and alerting. Re-run discovery on a schedule and alert on change: a new host, a newly opened port, a certificate about to expire, a new breach hit. Cadence matters; a weekly diff misses a lot.
- Validation. Confirm which exposures are actually exploitable instead of stopping at a CVSS number. This is where the market is moving fastest, and where most standalone EASM products are weakest because they have no testing engine behind them.
- Data residency. Almost every EASM product is SaaS-only. The vendor’s cloud holds a continuously updated map of your weakest external points. For many organizations that is acceptable; for defense, government, banks, and operators of critical infrastructure it is frequently not.
A 2026 study published by the EASM vendor IONIX found that organizations are typically aware of roughly 62 percent of their real external attack surface, with the rest hidden in subsidiaries and shadow IT. Gartner has predicted that organizations that prioritize security investments through a continuous threat exposure management (CTEM) program will be three times less likely to suffer a breach. Both numbers point the same way: the value is in continuous, validated coverage, not a one-time inventory.
The tools worth evaluating
Offensive360 ASM (part of the Offensive360 platform; on-premise or air-gapped)
Offensive360 ASM is the attack surface module of a unified application security platform that also includes SAST, DAST, mobile testing (MAST), an authorization-gated AI Pentester, and Autonomous Red Teaming. That architecture is the point: assets discovered by ASM are handed straight to the DAST engine or to a red-team operation for authorized validation, so “exploitable or not” is answered by the same platform that found the asset, with request and response evidence rather than a score.
Discovery combines passive sources, including certificate transparency, with active subdomain brute-forcing, host resolution, port and web-port probing, TLS and certificate posture, technology fingerprinting, DNS hygiene, and email-security checks (SPF, DMARC, DKIM, MTA-STS). Breached-credential monitoring correlates OSINT breach sources against the domains and mailboxes in scope. Every exposure is scored and rolled up into an organization-level External Exposure Risk that the dashboard shows separately from the findings-weighted Scan Risk Index of your applications. Named monitors run hourly or daily and alert by email on change.
The unusual property is deployment. The whole platform ships as a virtual appliance, an OVA for your own hypervisor or an Azure VHD image for your own cloud tenant, and it runs fully air-gapped. Your asset inventory, exposure records, and breach hits never leave your network. Pricing is flat, per project or per instance, with no per-asset meter, which matters because ASM asset counts only ever grow. See the ASM product page for the current capability list.
Palo Alto Networks Cortex Xpanse
Xpanse is the enterprise benchmark for internet-scale discovery, built on Palo Alto’s own continuous scanning of the public internet, and it is strongest inside the Cortex ecosystem, where discovered exposures can trigger automated response playbooks. It is a SaaS platform aimed at large, fast-changing estates. Buyers outside the Palo Alto stack should weigh how much of its value depends on the rest of Cortex, and note that surfacing an exposed port is not the same as demonstrating that it is exploitable.
Microsoft Defender External Attack Surface Management
Defender EASM inherits RiskIQ’s internet data and is the natural choice for Microsoft-centric security teams, particularly where licensing already covers it. Discovery starts from internet-visible assets and customer seeds and integrates with the wider Defender and Azure tooling. Its limits are the flip side of that: it is a Microsoft-native SaaS service, exploitability validation is not its focus, and organizations with significant non-Azure estates or complex subsidiary structures typically pair it with something else.
CyCognito
CyCognito pioneered “seedless” discovery: it infers what belongs to an organization from public data rather than relying on a customer-provided domain list, then ranks exposures with an attacker’s-eye view of exploitability. It has long market presence and analyst recognition. It is SaaS-only, and independent reviewers note that attribution can be less reliable for recently acquired subsidiaries; validate it against your own known-unknowns during a proof of concept.
Censys
Censys is the reference dataset for internet-scale scan data and certificate visibility, and its ASM product builds an attack surface view on top of that data. Teams that need raw breadth for research, threat hunting, or benchmarking another tool’s discovery get a lot from it. It is best understood as an internet data platform first: attribution, workflow, and validation typically require additional tooling around it. Pricing is quote-based on asset volume.
Tenable Attack Surface Management (Tenable One)
Tenable folds external discovery into its broader exposure management platform, which is attractive if Tenable already runs your internal vulnerability management and you want one prioritization model across both. The external module is a component of a larger platform rather than the centerpiece, so evaluate discovery depth and monitoring cadence specifically rather than assuming parity with the internal side.
runZero
runZero is a discovery specialist: unauthenticated, fingerprint-heavy discovery that reaches unmanaged, OT, and hard-to-identify assets internally as well as externally. If your gap is “we do not know what we own,” particularly in hybrid and industrial environments, it is one of the strongest options on this list. It is an inventory product rather than a validation product, and internal coverage is where it is most differentiated.
Rapid7 Surface Command, Mandiant Attack Surface Management, IONIX
Three platforms worth a look for specific needs. Rapid7 Surface Command combines external discovery with internal asset inventory (EASM plus CAASM) for teams that want one correlated asset graph. Mandiant ASM pairs discovery with frontline threat intelligence, so an exposure carries context about whether attackers are actually targeting that technology in the wild. IONIX focuses on mapping the digital supply chain, meaning third-party and infrastructure dependencies beyond the assets you directly own, and on validating exploitability of what it finds. All three are SaaS.
Detectify and Intruder
Both sit at the lean-team end of the market and are priced accordingly. Detectify is web-application focused, with a DAST heritage and crowdsourced payloads, and its entry plans cover a small number of subdomains. Intruder pairs vulnerability scanning with attack surface monitoring for teams that want a straightforward SaaS workflow. Neither offers on-premise deployment, entity mapping, or supply-chain coverage, and both should be evaluated as vulnerability-scanning-plus-monitoring rather than full exposure management.
Comparison
| Criterion | Offensive360 ASM | Cortex Xpanse | Defender EASM | CyCognito | Censys | Detectify / Intruder |
|---|---|---|---|---|---|---|
| Deployment | On-premise appliance (OVA or Azure VHD), air-gapped capable; cloud available | SaaS | SaaS | SaaS | SaaS | SaaS |
| Discovery | Passive (incl. CT logs) + active brute-force, ports, web ports, TLS, DNS, email security, tech fingerprints | Internet-scale vendor scanning | RiskIQ-derived internet data + seeds | Seedless inference + reconnaissance | Internet-wide scan data | Seed-based, web-focused |
| Breached credentials | Yes, correlated to in-scope domains and emails | Not a focus | Not a focus | Partial | No | Limited |
| Validation | Hand-off to DAST, AI Pentester, Autonomous Red Teaming in the same platform; proof-of-exploit evidence | Scored; response via Cortex playbooks | Scored | Exploitability-aware ranking | Data only | Web scanning |
| Monitoring cadence | Hourly or daily monitors with change alerts | Continuous | Periodic | Continuous | Periodic | Periodic |
| Subsidiary / supply-chain mapping | No (seed scope) | Limited | Limited | Yes (seedless) | No | No |
| Pricing model | Flat per project / per instance, no per-asset meter | Quote | Bundled with Microsoft licensing or quote | Quote | Quote by asset volume | Per-subdomain / per-target tiers |
Competitor characteristics reflect public vendor documentation and independent reviews as of 2026 and can change. Validate current capabilities and terms directly during procurement.
When Offensive360 is not the right choice
- You need seedless, organization-level entity mapping. If your problem is unknown subsidiaries after a decade of acquisitions, CyCognito or IONIX approach discovery from corporate structure outward. Offensive360 ASM starts from the domains and mailboxes you give it.
- You need digital supply-chain mapping. Tracing third-party and infrastructure dependencies beyond your own assets is IONIX’s specialty, not ours.
- Your gap is internal and OT inventory. runZero, or Rapid7 Surface Command’s combined view, address “what do we own inside the network” far better than an external ASM module.
- You want cloud-account connectors as the primary source. If you expect ASM to inventory every resource by reading your AWS, Azure, and GCP accounts directly, platform-native tooling or a CAASM product will fit better today.
- You are fully Microsoft-licensed and want a baseline. Defender EASM at zero incremental cost is a rational starting point for an Azure-centric estate.
Where Offensive360 fits best: organizations that cannot or will not let a SaaS vendor hold a live map of their weak points, teams that want discovery and validation in one platform instead of exporting a CSV from an ASM tool into a scanner, and buyers who prefer flat pricing over a per-asset meter.
Frequently asked questions
What is the difference between attack surface management and vulnerability scanning? Vulnerability scanning tests assets you already know about for known weaknesses. Attack surface management starts one step earlier: it discovers which internet-facing assets exist, including the ones nobody registered, and monitors that inventory for change. The two converge in platforms that validate what they discover; standalone ASM tools stop at a risk score.
How often should external discovery run? Daily is the practical floor for most organizations; hourly is worth it for large estates or during periods of change such as migrations and acquisitions. The important part is alerting on the diff, not the raw rescan, so a new host or port reaches a human within the same day.
Can attack surface management run on-premise or air-gapped? Discovery of internet-facing assets needs a path to the internet, but the platform, the inventory, and the exposure records do not have to live in a vendor cloud. Offensive360 ASM runs inside the customer’s own appliance, with egress restricted to the discovery it is performing, and stores everything locally. Fully offline deployments can run it against scoped internal seed data or via a controlled egress point.
What does “validated exposure” mean? That a safe, non-destructive test demonstrably confirmed the weakness, captured as a reproducible request and response, rather than a CVSS score inferred from a version banner. In Offensive360 that validation is performed by the same DAST engine, AI Pentester, or Autonomous Red Teaming operation that the ASM module feeds.
How is ASM priced? Most EASM vendors quote per asset, per seed, or per subdomain, so cost tracks the size of the surface you discover. Offensive360 is priced flat per project or per instance, with ASM included in the platform rather than sold as a separate module.
Next steps
- Book a demo and we will run discovery against a domain you choose, then validate one of the exposures live.
- Read the ASM product page, or see how ASM feeds Autonomous Red Teaming and the DAST engine.