Attack Surface Management Tools: A Buyer’s Guide.

An ASM tool answers a simple question: what of ours can an attacker see and reach? External attack surface management (EASM) looks from the outside, as an attacker would. Internal tools list assets from inside the network. Many buyers start with the external view because it can find forgotten systems.

For background, read EASM 101.

They complement each other. If you can afford one first, choose the view that shows what you do not know about.

• Discovery: does it find assets you did not list, such as old subdomains or cloud buckets?
• Accuracy: are the assets really yours, or does it list partners and noise?
• Context: does each finding show owner, technology and why it matters?
• Prioritization: is the ranking explained, and does it use exposure and exploit information?
• Freshness: how often is the picture updated?
• Workflow: can findings go to ticketing and to the right owner?

Run the trial long enough to see change. Add a new subdomain or a test storage bucket on purpose during the trial and note how soon each tool reports it. This planted-asset check shows freshness better than any claim. Also ask each vendor to explain, for five assets it found, why it believes they are yours. Clear reasoning is a good sign; a bare list is not.

• How is ownership of an asset decided and corrected?
• Which cloud and SaaS sources are covered?
• Does it check for leaked credentials or data tied to the assets?
• How are new assets reported, and how fast?
• Is there an API for all data?
• What happens when scanning could affect a fragile system?

The RFP question list has an EASM section you can copy.

Ask also for a sample export of findings, so you can check that fields such as owner, first seen date and evidence are present before you sign.

CISA maintains a catalog of known exploited vulnerabilities. A good tool should let you see which of your exposed assets run software on that list. See known exploited vulnerabilities in the glossary. The NIST Cybersecurity Framework also lists asset management under its Identify function, which is a useful anchor for your criteria.

• Treating the first scan as the answer. The picture changes every week as teams add services and domains.
• Not agreeing asset ownership. A finding without an owner is never fixed.
• Counting findings, not risk. A long list with no ranking wastes time.
• Scanning without care. Some systems are fragile, so agree rules for testing.
• Leaving out cloud and SaaS. Many exposures live there, not on classic servers.

Include IT, security and the business owner of each major system in the trial, since fixes need all three.

A tool is only useful if findings reach people who can act. Decide how each type of finding is routed: a forgotten test server goes to its team, an expired certificate to the web team, an exposed storage bucket to the cloud owner. Set a target time for each level of risk and report on progress every month.

Link the tool to ticketing so that each finding becomes a task with an owner and a due date. Track how many exposures are new, how many were closed and how many are accepted risks with a written reason. A falling number of new exposures is a sign that processes are improving, not only that tickets are being closed.

When a major vulnerability is announced, use the tool to ask a simple question: which of our exposed systems run the affected software? The answer should take minutes, not days.

Write down what good looks like after three months: for example, every internet-facing system has a named owner, and new exposures are reviewed within the time you set. Define your own targets; do not copy numbers from a vendor brochure.

Short definitions of the words used above, so that everyone in the buying team reads them the same way.

• Attack surface. All the systems, domains, services and accounts of your company that an attacker could reach.
• Asset. Anything you own or run that is connected: a server, a domain, a cloud account, an app.
• Shadow IT. Systems used or set up without the IT team knowing.
• Subdomain. A name under your main domain, such as an old test site, that is easy to forget.
• Exposure. A weakness that can be reached from outside, such as an open service or a leaked key.
• Seed. The starting data you give a tool, usually your main domains and company names.
• Attribution of an asset. The decision that an asset really belongs to you, which a good tool explains.

Brandefense offers External Attack Surface Management as one of the three pillars of its platform, next to cyber threat intelligence and digital risk protection. Third-party risk is a module of External Attack Surface Management. See the attack surface reduction use case and the vulnerability and exposure management page. Add it to your trial like any other candidate, or Request a demo.

These public bodies are the references behind the criteria in this guide. Open them and cite the exact page you rely on in your own paper.

• NIST Cybersecurity Framework: the six functions and the outcomes under each.
• ENISA: European threat landscape reports and guidance.
• CISA: advisories and the catalog of known exploited vulnerabilities.
• OWASP: open guidance and tools for software security.