Contract Senior Security Engineer: Azure & SIEM

Flagstone Group; Greater London; Hybrid; GBP 90,000 - 120,000; Full time

Job summary

Flagstone Group is seeking a senior security engineer to own and enhance cloud security, SIEM, and threat detection across Azure. You will operate Sentinel, Defender for Cloud, and contribute to detection-as-code.

The role emphasizes hands-on leadership, impact, and coordinating security across engineering squads. The ideal candidate brings deep SIEM expertise, strong Azure security experience, and experience with Terraform or Bicep in a fintech environment.

Qualifications

• Hands-on SIEM experience with Microsoft Sentinel or equivalent.
• Azure security experience across Defender for Cloud, Entra ID, and Azure networking.
• IaC experience using Terraform or Bicep in security engineering context.
• Experience driving vulnerability remediation cycles with engineering squads.
• Familiarity with data-loss-prevention controls.
• Knowledge of AI security considerations and securing AI workloads.
• Ability to contribute to threat modelling and communicate risk clearly to engineering and product teams.
• Growth mindset and curiosity to keep learning.
• SC-200 certification verified.
• KQL proficiency for detection rule authoring and threat hunting.
• Experience in a fintech or financial services environment.

Responsibilities

• Own and operate alerting and monitoring capability through a transition period.
• Maintain and improve Microsoft Sentinel deployment: tuning rules, managing data connectors, reducing alert noise.
• Operate Defender XDR and Defender for Cloud: policy management and posture recommendations.
• Maintain and extend automated security checks in delivery pipelines (shift-left).
• Drive down time-to-fix on known vulnerabilities with engineering squads.
• Support data-loss-prevention controls to reduce data leakage risk.
• Support safeguards around AI usage, including securing AI workloads and data exposure.
• Investigate suspicious activity surfaced through Sentinel and Defender: triage, elevate, or contain.
• Support incident response: containment, evidence gathering, post-incident review.
• Contribute to detection-as-code and infrastructure-as-code (Terraform or Bicep).
• Coordinate penetration test engagements and work with teams to prioritize remediation.

Skills

SIEM experience

Microsoft Sentinel

Azure security

Terraform

Bicep

Vulnerability remediation

Data-loss-prevention

AI security

Threat modelling

KQL

Fintech/financial services experience

Education

SC-200 certification

Tools

Terraform

Bicep

Job description

Flagstone Group is seeking a senior security engineer to own and enhance cloud security, SIEM, and threat detection across Azure. You will operate Sentinel, Defender for Cloud, and contribute to detection-as-code.

The role emphasizes hands-on leadership, impact, and coordinating security across engineering squads. The ideal candidate brings deep SIEM expertise, strong Azure security experience, and experience with Terraform or Bicep in a fintech environment.