What is a Fractional CISO?

A fractional CISO (Chief Information Security Officer) is a senior security executive — typically 15+ years in cybersecurity leadership roles — who provides part-time strategic security oversight to multiple organisations, usually 2–4 days per week each. UK fractional CISO day rates sit between £1,200 and £2,000 per day, with the average around £1,600, depending on sector complexity, compliance requirements, and executive experience. The fractional CISO model has grown significantly in the UK since 2022 because three market forces converged: the acute shortage of senior security talent (ISACA reports 3.5m unfilled cybersecurity roles globally), regulatory pressure requiring board-level security oversight, and SME recognition that a £150k permanent CISO salary often exceeds the actual volume of executive security work at sub-£50m revenue companies.\n\nThis guide covers what UK fractional CISOs actually do in 2026, what they cost versus permanent hires, typical engagement models, and how to evaluate senior security leadership candidates. It is written for three audiences: CEOs and boards considering fractional versus permanent CISO appointments; senior security professionals evaluating fractional CISO careers; and technology leaders determining whether fractional security leadership fits their business stage.