Onsite SIEM Analyst

About the job youre considering

Role is based onsite in Wokingham 5 days per week.

Embedded within an existing Customer SOC, Capgemini supply a level of cyber expertise and corporate experience, assisting the customer in regular SOC activities, as well as proposing new processes and bringing 'best practice' to the workplace. The position is office based.

We are seeking a high-calibre Cyber Security Operations Centre (CSOC) Analyst to monitor and respond to threats in a Critical National Infrastructure (CNI) environment supporting essential energy operations. You will be responsible for real-time security monitoring, triage, investigation, and early incident response, working with security monitoring and incident/event management platforms to identify suspicious activity, validate alerts, and escalate confirmed incidents. This is an operational role requiring strong technical judgement, clear written communication, and the ability to remain effective under time pressure.

You will also contribute to continuous improvement by capturing lessons learned from incidents, helping tune detections, and strengthening procedures and documentation.

Your role

• Monitoring & triage - Monitor security events and alerts using industry-standard SIEM / incident & event management platforms (e.g., Elastic, Microsoft Sentinel, Splunk). Perform rapid triage to determine alert validity, severity, scope, and potential business/operational impact. Correlate related events and identify patterns across multiple alerts to reduce duplication and improve incident clarity.

• Investigation & evidence-led analysis - Conduct investigations across endpoint, identity, network and log telemetry; build timelines and hypotheses grounded in evidence. Maintain high- quality investigation records, including the key evidence and the queries/search logic used to reach conclusions (to support peer review, auditability, and reliable handover). Apply foundational host- based forensic concepts (e.g., process ancestry, persistence artefacts, lateral movement indicators, log integrity considerations)

• Incident response & escalation - Handle security incidents from initial identification through to handover to incident management / incident response, ensuring escalations are timely, complete, and actionable. Support containment/mitigation activities where authorised (e.g., coordinating response actions with relevant teams and tooling).

• Continuous improvement & PIR learnings - Custom rule creation: develop and fine-tune detection rules and alerts to identify malicious activity; validate effectiveness and reduce false positives. Identify and implement lessons learned from incidents and post-incident reviews (PIRs) to improve processes, runbooks, and detection logic. Contribute to a culture of quality and standardisation by improving documentation and operational practices.

You can bring your whole self to work. At Capgemini building an inclusive future is part of everyday life and will be part of your working reality. We have built a representative and welcoming environment, for everyone.

Your skills and experience

• Strong knowledge of Linux and Windows operating systems and core networking concepts and technical communication skills with excellent written communication (clear, structured incident notes and stakeholder updates). Demonstrable experience working effectively in time-pressured operational environments.

• Strong foundational knowledge of incident and event management / SIEM platforms (e.g., Elastic / Sentinel / Splunk) and knowledge of query languages used for investigations and detections (e.g.,Kusto Query Language (KQL), ES|QL, Kibana Query Language).

• Strong knowledge of Endpoint Detection & Response (EDR) concepts and workflows and knowledge of IDS/IPS concepts and signature-based detection principles.

• Understanding of attacker Tactics, Techniques and Procedures (TTPs) and how they manifest in logs/telemetry and evidence of keeping up to date with threat trends, attacker tradecraft, and emerging defensive techniques.

• Experience handling incidents…