External ISO / CISO as a Service: when and why the role makes sense

2026-07-11 · by SECURITYSQUAD

Information security needs a named, accountable role – not just technology. Organisations that cannot or do not want to fill this role in-house bring in an external Information Security Officer (ISO). This guide explains what the role stands for, when it becomes mandatory, and why an external ISO – often called CISO as a Service – is frequently the most pragmatic option for mid-sized companies and the public sector.

What does an information security officer do?

The Information Security Officer (in Germany the Informationssicherheitsbeauftragter, ISB; internationally the CISO – Chief Information Security Officer) is the central specialist function for all information security matters in an organisation. This role does not own a single firewall; it owns the framework in which security is governed. Core responsibilities include:

Building and maintaining an ISMS (information security management system) per ISO 27001 or BSI IT-Grundschutz
Advising management on all information security matters – including risk assessment and decision papers
Risk management: identifying and assessing threats and prioritising measures
Policies and processes: developing, introducing and monitoring their compliance
Security incidents: analysing, coordinating and learning from them
Awareness and training for employees
Audits and evidence: preparing and supporting them

Importantly, the ISO steers and controls; it does not implement every technical measure itself. That is why the role should report directly to top management – not sit inside the IT department. Otherwise a conflict of interest arises, because the same function would both implement measures and review them.

Why the role is becoming necessary

Regulation and standards increasingly require a named accountable person for information security:

ISO 27001 presupposes a governed ISMS with clear responsibilities – without a named role there is no robust management system.
BSI IT-Grundschutz defines the ISO as a fixed function of security management.
NIS2 moves information security to board level: management must establish and monitor risk management and answer for it. That is hard to deliver without a professionally accountable role.
For critical infrastructure (KRITIS) operators an information security officer is mandatory anyway.

Even without a direct legal obligation, the pressure grows: customers, clients and supply chains request security evidence, and insurers expect structured security processes. A named role is therefore a baseline requirement rather than a nice-to-have.

In-house or external – weighing it up

Whether to fill the role internally or contract it out depends on capacity, know-how and structure.

In favour of an internal ISO:

proximity to in-house processes, culture and people
constant availability and quick coordination
knowledge stays within the organisation long term

Typical obstacles for mid-sized companies:

Resources: a suitable full-time hire is expensive and scarce on the market.
Know-how: the role demands broad, up-to-date knowledge of standards, law and technology – hard to build up on the side.
Conflict of interest: if the ISO comes from IT, they effectively review their own work.
Objectivity: internal proximity can cloud the critical, independent view.

By contrast, an external ISO offers:

immediately available, broad expertise without a long ramp-up
independence and objectivity – an impartial outside view
predictable costs instead of an expensive permanent hire
experience from many projects and industries

The trade-off: an external ISO is not permanently on site and must first understand the company's context. Good collaboration and fixed points of contact offset this.

When an external ISO / CISO as a Service makes sense

CISO as a Service means buying the ISO role as a service – with defined responsibility, but without creating a permanent position. It is especially worthwhile when:

you are an SME or public authority for which a full-time role would be uneconomical
capacity or expertise is missing in-house
you are in the start-up phase of an ISMS or an ISO 27001 project and need experienced steering
you deliberately want objectivity and independence from outside
a vacancy needs to be bridged at short notice

How the model works in practice

An external ISO is formally appointed and takes on the role with a clearly defined scope of tasks and responsibility. In practice this means:

Baseline assessment: capturing protection needs, risks and existing measures.
Building and steering the ISMS: establishing policies, processes and evidence.
Ongoing operation: recurring assessments, reports to management, audit support, incident response.
Collaboration: a fixed point of contact, defined presence and availability, close coordination with IT and business units.

Overall accountability for information security always remains with management – but the external ISO takes on the specialist role with full responsibility for the assignment.

Selection criteria for an external ISO

When choosing, look for:

demonstrable qualification in ISO 27001 and BSI IT-Grundschutz
vendor neutrality – advice free of product interests
experience in comparable industries and organisation sizes
clear acceptance of responsibility rather than mere recommendations
understandable communication up to board level
reliable availability and defined collaboration

The external ISO at SECURITYSQUAD

SECURITYSQUAD offers the external ISO (CISO as a Service) on a vendor-neutral basis and with full responsibility for the assignment taken on. We work on the basis of ISO 27001 and BSI IT-Grundschutz, and support ISMS setup, NIS2 implementation and certification preparation. Founded in 2022, certified to ISO 27001 (on the basis of IT-Grundschutz) and ISO 9001, and a member of the Alliance for Cyber Security, we bring the role into your organisation in a structured, objective and audit-proof way.

Wondering whether an external ISO is the right path for you? We help you assess the need and set up the role to fit your organisation.