altdns vs Assetnote ASM: 2026 Comparison
altdns is a free external attack surface management tool. Assetnote ASM is a commercial external attack surface management tool by Assetnote. Compare features, ratings, integrations, and community reviews side by side to find the best external attack surface management fit for your security stack.
CST VerdictBased on our analysis of NIST CSF 2.0 coverage, core features, company size fit, deployment model, here is our conclusion:
Security teams hunting for overlooked subdomains in external attack surface reconnaissance will find altdns invaluable because it generates permutations that standard enumeration tools miss, catching typosquatting and subdomain variations that land in your blind spots. The 2,439 GitHub stars reflect adoption by practitioners who've validated the mutation logic against real-world domain configurations. Skip this if you need a managed UI or integration with your existing EASM platform; altdns is a CLI-first tool that demands operator familiarity and manual orchestration into your scanning workflow.
Mid-market and enterprise security teams managing sprawling external infrastructure will get the most from Assetnote ASM because its hourly asset discovery actually catches exposures before your business units spin up new services, not weeks after. The platform covers ID.AM and DE.CM across NIST CSF 2.0, meaning you're building a real asset inventory while monitoring it continuously, and the exploit-based verification eliminates the noise that buries actionable findings in traditional scanners. Skip this if your organization lacks the headcount to operationalize a workflow-driven program; Assetnote's strength is enabling lean teams to prioritize, not giving you a dashboard to ignore.
