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Cybersecurity · head to head

Diligent vs Tenable Nessus

Diligent logo

Diligent

Cybersecurity

Board management and enterprise GRC platform assembled from Galvanize, Steele and Diligent Boards

From
On request
Rated
-
Full reviewWebsite
Tenable Nessus logo

Tenable Nessus

Cybersecurity

Network vulnerability scanner

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only Tenable Nessus has a free tier, so it costs nothing to try first.
  • Each has a real cost: Diligent the platform is an assembly of acquisitions, with the analytics engine from ACL, risk from Rsam, ethics and third-party diligence from Steele and the board portal from Diligent itself, so cross-module reporting and consistent user experience should be tested in a proof of concept rather than assumed.; Tenable Nessus nessus Professional is $4,790 for one year, sold as an annual licence rather than a per scan or usage based fee
  • They diverge on capability: Diligent covers Diligent Boards, Tenable Nessus covers Network scanning.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Diligent and Tenable Nessus actually diverge.

Attributes where Diligent and Tenable Nessus differ
AttributeDiligentTenable Nessus
Starting priceOn requestFree
Pricing modelquotesubscription
Free tierNoYes
PlatformsWeb, iOS, Android, WindowsWindows, Linux, Macos, Cloud
FoundedUnknown2002

Identical on both: user rating (Not yet rated), category (Cybersecurity).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Diligent

  • Diligent Boards
  • Entity management
  • Audit and analytics
  • Risk management
  • Third-party risk
  • Ethics and compliance
  • ESG and sustainability
  • Market intelligence

Only in Tenable Nessus

  • Network scanning
  • Vulnerability detection
  • Configuration assessment
  • Malware detection
  • Compliance checking
  • Cloud security assessment
  • Mobile scanning
  • API access

What people use each for

The jobs each tool is most often brought in to do.

Diligent

  • A listed company that wants board papers, entity records and the audit committee reporting pack produced from one governance systemnot Tenable Nessus
  • An internal audit function moving from sampling to full-population transaction testing using the ACL heritage analytics enginenot Tenable Nessus
  • A regulated firm consolidating a whistleblower hotline, third-party due diligence and policy attestation after an enforcement findingnot Tenable Nessus
  • A group needing sustainability disclosure data collected with the same audit trail and controls as financial reportingnot Tenable Nessus

Tenable Nessus

  • Vulnerability scanning of servers, network devices and web applicationsnot Diligent
  • Configuration and compliance auditing against hardening benchmarksnot Diligent
  • Point in time assessments by consultants and penetration testersnot Diligent

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Diligent

  • The platform is an assembly of acquisitions, with the analytics engine from ACL, risk from Rsam, ethics and third-party diligence from Steele and the board portal from Diligent itself, so cross-module reporting and consistent user experience should be tested in a proof of concept rather than assumed.
  • Pricing is unpublished and consistently at the top of the market, and organisations that need only one capability, a board portal or an audit analytics tool, generally pay less and get more from a specialist.
  • Renewal leverage is weak once the board portal is embedded, because directors are the least willing user group to be migrated and that dependency is well understood by the vendor at renewal time.
  • The analytics engine expects real data skills, and audit teams without an analytics-capable member typically use a fraction of what they licensed while paying for all of it.
  • Module-by-module implementation means the promised single view of governance and risk usually arrives years after the first purchase, if the later modules are ever funded.

Tenable Nessus

  • Nessus Professional is $4,790 for one year, sold as an annual licence rather than a per scan or usage based fee
  • Support beyond the base entitlement costs an extra $400 per year for Advanced Support with 24x365 phone and chat access
  • The on demand training course is a separate $275 purchase for a single person for one year
  • Multi year discounts require paying for two or three years up front

Pricing, plan by plan

Diligent

On request
  • Diligent One Platform$undefined/year
    • Quoted by module and user count
    • Board portal seats priced separately from GRC modules
    • Annual subscription, commonly multi-year

Tenable Nessus

Free
  • Nessus EssentialsFree
    • Up to 16 ips
    • Network scanning
    • Vulnerability assessment
  • Nessus Professional$2600/year
    • Unlimited targets
    • Enterprise features
    • Advanced analytics
  • Nessus Expert$5200/year
    • All Professional features
    • Cloud integration
    • Advanced reporting

Which should you pick?

Choose Diligent if

  • You need diligent boards.
  • You work on Web, iOS, Android, Windows.
  • You also want entity management.
Diligent review

Choose Tenable Nessus if

  • You need network scanning.
  • You want to start without paying.
  • You work on Windows, Linux, Macos, Cloud.
  • You also want vulnerability detection.
Tenable Nessus review

Questions people ask

Is Diligent or Tenable Nessus better?
Neither clearly leads. Diligent starts at On request and Tenable Nessus at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Diligent or Tenable Nessus?
Tenable Nessus has a free tier; the other does not. Paid plans start at On request for Diligent and Free for Tenable Nessus.
Does Diligent or Tenable Nessus run on more platforms?
Diligent runs on Web, iOS, Android, Windows. Tenable Nessus runs on Windows, Linux, Macos, Cloud.
Can I use Tenable Nessus for free?
Yes. Tenable Nessus has a free tier, so you can try it without paying. Diligent starts at On request.
What is Diligent best used for?
Diligent is most often used for a listed company that wants board papers, entity records and the audit committee reporting pack produced from one governance system, an internal audit function moving from sampling to full-population transaction testing using the acl heritage analytics engine, a regulated firm consolidating a whistleblower hotline, third-party due diligence and policy attestation after an enforcement finding, a group needing sustainability disclosure data collected with the same audit trail and controls as financial reporting. Of those, a listed company that wants board papers, entity records and the audit committee reporting pack produced from one governance system and an internal audit function moving from sampling to full-population transaction testing using the acl heritage analytics engine are not what Tenable Nessus is typically brought in for.
What can Diligent do that Tenable Nessus cannot?
Diligent covers Diligent Boards, Entity management, Audit and analytics, Risk management. Tenable Nessus covers Network scanning, Vulnerability detection, Configuration assessment, Malware detection.

Answered from the vendors’ own pages

Diligent: Is Diligent One the same product as Galvanize?

It contains it. Diligent bought Galvanize, the ACL and Rsam merger, for around one billion dollars in April 2021, and its audit analytics and risk modules are that heritage rebranded into Diligent One.

Tenable Nessus: What are the three Nessus offerings?

Nessus Essentials is a free introductory offering for educators, students, and career starters, limited to 16 IPs for scanning. Nessus Professional is designed for consultants and SMBs, providing unlimited IT scans across any location. Nessus Expert is the premium offering extending Professional with web application scanning, infrastructure-as-code scanning, and external attack surface assessment up to 5 domains.

Source
Diligent: What does Diligent cost?

Not published. It is quoted by module and user, and board portal seats are priced differently from GRC seats. Expect an annual or multi-year enterprise agreement.

Tenable Nessus: What OS platforms does Nessus support?

Nessus runs on Debian/Kali Linux, Fedora, FreeBSD, Mac OS X, Red Hat/CentOS, SUSE Linux, Ubuntu, and various Windows versions including Server 2008, 2012, and Windows 7-10.

Source
Diligent: Can you buy just the board portal?

Yes, Diligent Boards is sold on its own and is the most common entry point. The GRC modules are separate purchases.

Tenable Nessus: Can I use Nessus to scan third-party networks as a consultant?

Yes, Tenable permits you to use Nessus to scan third-party networks. Nessus Professional is ideal for consultants.

Source
Diligent: Does it replace a SOC 2 automation tool?

No. Diligent is aimed at enterprise audit, risk and governance, not at automated evidence collection for security certifications.

Tenable Nessus: Can Nessus perform PCI external scanning?

Yes, you can use Nessus Professional to perform external network scans as required by the PCI DSS 11.2.2 requirement.

Source
Tenable Nessus: What additional features does Nessus Expert provide?

Web application scanning, which is dynamic application security testing (DAST) providing comprehensive visibility and insight into web application security issues; scanning code repositories for vulnerabilities; and assessing external attack surface with subdomain discovery.

Source
Tenable Nessus: What support options exist for Nessus Professional?

Standard Support includes software upgrades, patches, plugin access, and 24x7 support via chat and community portal. Advanced Support adds 24x7 phone access and committed SLAs: P1 less than 2 hours, P2 less than 4 hours, P3 less than 12 hours, P4 less than 24 hours.

Source
Tenable Nessus: How frequently are Nessus plugins updated?

Nessus plugins are updated daily, based on when vendors and security research sites publish new vulnerabilities.

Source
Tenable Nessus: How does licensing work in virtual machine environments?

Whether you are using Nessus in a physical or a virtual environment, the IP addresses or hosts that you are scanning from must be licensed.

Source
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