Nessus
Pros
- Authenticated scanning of internal assets (workstations, network devices).
- Widely accepted for compliance and audit reporting (e.g., PCI DSS).
Cons
- Core strength is infrastructure, not application security.
- Nessus Professional (the standalone scanner) lacks central management, scan scheduling, and enterprise reporting; these require an upgrade to Tenable.io or Tenable.sc.
- Un-credentialed or black-box scans are primarily signature-based, which can generate a high volume of false positives and noise for AppSec teams to triage.
Detectify
Pros
- Payload-based testing confirms exploitability, which significantly reduces false positives and the AppSec team’s triage workload.
- Vulnerability sourcing from a private community of ethical hackers and an AI researcher (Alfred) finds novel, 0-day, and non-CVE vulnerabilities.
- Deep, dynamic API fuzzing engine.
Cons
- Not an internal network scanner
- Does not offer an on-premise or agent-based solution.
- Focus is entirely on the external attack surface, so it won’t find internal host-level misconfigurations or patch-level compliance issues.
In-depth comparison: Visibility and Context
This is a fundamental point of difference. Nessus and Detectify are built to provide two distinct types of visibility and context.
Nessus excels at deep, host-level context for known assets. Its primary function is internal vulnerability management. You provide it with IP ranges and, ideally, credentials. The context it returns is granular: exact OS versions, running services, patch levels, and file permissions. This is essential for auditing internal infrastructure and driving a patch management program. While newer tiers add EASM capabilities to find unknown assets, the core of Nessus is designed to audit what you already know you have.
Detectify starts from the outside in, built on a foundation of external visibility. It’s designed to answer the questions Nessus doesn’t: “What web applications do I have exposed to the Internet?” and “What is their business purpose?” This is a different, and often harder, problem than scanning a known IP range.
Detectify provides context through:
- First, Continuous Asset Discovery constantly monitors and identifies your internet-facing domains, subdomains, and web applications, moving beyond a simple IP-based view.
- Second, it applies Asset Classification to provide insight into the purpose of these assets, not just their OS version or running services.
- Finally, based on this discovery and classification, Detectify provides intelligent Scan Recommendations, highlighting the high-risk, high-value web applications you may have missed.
In short, Nessus tells you everything about the hosts you know. Detectify discovers and provides business context for the web applications you’ve forgotten, so you know what to protect.
In-depth comparison: Assessment
The assessment methodology is the most significant technical differentiator.
Nessus operates on a plugin-based, signature-matching model. When it scans an asset, it identifies the technology and version (e.g., “Apache v2.4.53”) and reports all known CVEs associated with that version. This is highly effective for known vulnerabilities but has two consequences for an AppSec team:
- High Triage Load: It shifts the burden of proof to the user. The AppSec team must manually validate if a “potential” vulnerability is actually present and exploitable in their specific configuration.
- Limited to “Knowns”: Its coverage is primarily dependent on publicly available tests and CVEs.
Detectify is engineered to solve these problems by using payload-based testing. It emulates a real-world exploit by executing a non-destructive payload. A finding is only triggered if the payload resolves, which confirms the vulnerability is actively exploitable.
This approach provides two key benefits:
- Reduced Triage Workload: It provides a high-confidence, confirmed vulnerability, allowing the AppSec team to focus on remediation rather than validation.
- Finds Novel Threats: Detectify’s vulnerability sourcing is a multi-source model. It combines an internal research team, an AI researcher (Alfred), and a private crowdsourced community of elite ethical hackers. This allows Detectify to generate tests for novel, emerging, and non-CVE vulnerabilities that signature-based scanners will miss.
API Assessment
- Nessus: The Nessus Expert tier provides API scanning. This allows it to run a set of checks for common vulnerabilities, typically against a provided OpenAPI (Swagger) schema. This is effective for identifying known issues in a defined API.
- Detectify: Detectify’s API scanner is built on a proprietary engine designed for dynamic fuzzing. Instead of just running a static set of checks, it probes the API with randomized and rotated payloads with every scan. With a massive library of variations (e.g., 330,000+ payloads for command injection), it is designed to discover vulnerabilities that static checks would miss, even on an unchanged target.
The speed at which a scanner can test for new and emerging web threats is another key differentiator.
Nessus primarily relies on its internal vulnerability research and the rule sets provided in its plugins. The coverage is dependent on the update cadence of those plugins, which are comprehensive for known infrastructure CVEs.
Detectify utilizes a multi-source model for generating security tests. This combines an internal security research team, a private crowdsourced community of elite ethical hackers, and an automated AI system called Alfred. This system uses LLMs to parse newly disclosed CVEs, prioritizes them based on exploitability using the EPSS framework, and attempts to auto-generate payload-based tests from public proofs-of-concept. These tests are then human-verified.
The goal of this multi-source approach is to significantly reduce the time-to-test for relevant, exploitable web CVEs as they emerge, and to find novel, non-CVE vulnerabilities that signature-based scanners will miss.
Finally, how are APIs considered in assessment capabilities?
Nessus’s strength is identifying the underlying infrastructure. It can detect the service running on an API port, find its version, and report associated infrastructure CVEs.
Detectify, however, built its API scanner on a proprietary engine designed specifically to move beyond static checks. Instead of just running a static set of checks, it probes the API with randomized and rotated payloads with every scan. With a massive library of variations (e.g., 330,000+ payloads for command injection), it is designed to discover vulnerabilities that static checks would miss, even on an unchanged target.
This methodological difference is critical. Nessus’s scan provides a consistent but infrastructure-level assessment. Detectify’s dynamic approach provides continuous discovery, probing the API in new ways with each run to find vulnerabilities that static, signature-based checks would miss.
In-depth comparison: Usability
Nessus Professional is praised for its “point and shoot” simplicity, but this applies to a specific, point-in-time use case. An engineer can easily install the software and launch a scan against a set of known IPs or ranges. It’s built to be a powerful tool in the hands of an individual practitioner for an assessment.
The usability challenge for an AppSec team emerges after the scan. The high volume of “potential” findings from its signature-based scans can be overwhelming. The Nessus Pro reports are functional for an auditor or a systems administrator focused on patch management, but they are not designed for a continuous AppSec remediation workflow.
Detectify is designed from the ground up for a modern AppSec workflow
Users can get started within minutes. The primary onboarding flow involves connecting cloud providers to enable Surface Monitoring, our attack surface assessment tool, for continuous monitoring of the external attack surface. For users with complex needs, like testing custom-built web applications, the onboarding process supports this with more technical granularity, reflecting its focus on application-level testing. This involves creating “scan profiles” and, for authenticated testing, configuring credentials and login sequences.
This setup is geared toward a technical user, and its core usability strength is the actionability of its findings. Because findings are payload-based and confirmed exploitable, they provide a high-confidence signal. Every finding is reproducible and built for a technical AppSec audience, not just compliance. This significantly reduces the time AppSec teams spend triaging noise and allows them to focus on remediation.
Conclusion: Which product should I choose?
This choice depends entirely on the problem you need to solve, as they are built fundamentally different.
Nessus is the standard for internal vulnerability management. Its core function is to scan known IP ranges (like your internal servers, employee laptops, and office networks) and provide deep, host-level context. It excels at answering the question, “Are my known servers and workstations patched?” by identifying OS versions, running services, and patch levels based on signatures. This is essential for internal compliance, auditing, and driving a patch management program.
Detectify, in contrast, is designed to answer the AppSec question, “What web applications do I have exposed to the internet, and are they actually exploitable?” It starts by discovering your external-facing domains and web apps, including those you’ve forgotten. Crucially, it uses payload-based testing to confirm vulnerabilities, which provides high-confidence, actionable findings with a low false-positive rate. If your priority is to find exploitable web and API vulnerabilities on your perimeter and reduce your team’s triage workload, Detectify is the correct choice.
