Senior Security Engineer

Salary: £72,000 - 97,000 per year

Requirements:

• Hands-on SIEM experience, ideally Microsoft Sentinel; equivalent platforms such as Splunk, Chronicle, or QRadar are considered.
• Practical Azure security experience across Defender for Cloud, Entra ID, Azure networking, and cloud security posture management.
• Experience writing infrastructure-as-code using Terraform or Bicep in a security engineering context.
• Experience driving vulnerability remediation cycles with engineering squads.
• Familiarity with data-loss-prevention controls.
• Familiarity with AI security considerations, including securing AI workloads and data exposure risks, and/or using AI tooling to augment security engineering workflows.
• Ability to contribute to threat modelling and communicate security risk clearly to engineering and product audiences.
• A growth mindset and genuine curiosity to keep learning.
• SC-200 (Microsoft Security Operations Analyst) certification.
• KQL proficiency for detection rule authoring and threat hunting.
• Experience working in a similar fintech or financial services environment.

Responsibilities:

• Own and operate our alerting and monitoring capability through a transition period, keeping detection and response steady.
• Maintain and improve our Microsoft Sentinel deployment, including writing and tuning detection rules, managing data connectors, and reducing alert noise.
• Operate and optimise Defender XDR and Defender for Cloud, including policy management and posture recommendations.
• Maintain and extend automated security checks in our delivery pipelines.
• Drive down time-to-fix on known vulnerabilities, coordinating remediation with engineering squads.
• Support data-loss-prevention controls that reduce the risk of sensitive data leaving the business.
• Support safeguards around how the business accesses and uses AI, including securing AI workloads and their data exposure.
• Investigate suspicious activity surfaced through Sentinel and Defender, including triage, escalation, or containment as appropriate.
• Support incident response, including containment, evidence gathering, and post-incident review.
• Contribute to detection-as-code and infrastructure-as-code using Terraform or Bicep for security tooling.
• Coordinate penetration test engagements, including scope, logistics, and findings review, and work with engineering teams to prioritise remediation.

Technologies:

• AI
• Azure
• Cloud
• Support
• Security
• Splunk
• Terraform

More:

We are Flagstone, an online savings platform reinventing how individuals, businesses, and charities manage, protect, and grow their cash. We are a diverse, collaborative, and profitable business where smart people do their best work. Our culture is built on kindness, respect, growth, and inclusion, and we believe in giving people room to develop and make a visible impact. Our Security Engineering team is small but broad in scope, covering cloud security, detection, and security operations directly in our Azure estate. The team runs Microsoft Sentinel, Defender XDR, and Defender for Cloud, manages tooling through infrastructure-as-code, and continuously builds out our detection and response capability. This is a contract role based in our London office, working in a hybrid setup within our Engineering department.

last updated 35 week of 2026