Knock vs SurfaceDiff: Side-by-Side Comparison (2026)
Features, pricing, ratings, and pros and cons, compared head to head.
Knock is a free external attack surface management tool. SurfaceDiff is a commercial external attack surface management tool by SurfaceDiff. Compare features, ratings, integrations, and community reviews side by side to find the best external attack surface management fit for your security stack. Independent and vendor-neutral: our scores and rankings are earned, never bought — sponsored placement is always labeled.
CST VerdictBased on our analysis of NIST CSF 2.0 coverage, core features, company size fit, deployment model, here is our conclusion:
Security teams doing external attack surface reconnaissance on a budget should start with Knock; it's free, it works, and the 4,054 GitHub stars reflect actual adoption rather than marketing hype. The tool excels at the narrow job of subdomain enumeration, which maps NIST Govern and Identify functions by forcing you to know what's actually exposed before you can defend it. Skip Knock if you need continuous monitoring or API integration into your existing ASM stack; this is a point-in-time scanner you run manually, not a platform that feeds ongoing discovery into your risk register.
Data verified Sep 2026
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