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Senior Security Engineer

Date: 04-Jan-2023

Location: SLOUGH, GB

Company: Telefonica S.A.

Location: Northampton/Slough/Reading



It matters to us that Team O2 is as diverse as the communities we serve. 

We welcome and encourage people from all backgrounds to apply.   

Whoever you are, O2 has a place for you. 

Come join us.


About the Role:

The Security Engineering Team supports the security tools used by Security Operations in maintaining security of the business. These include Security Incident & Event Management systems, end user and perimeter protection tools.


The role of a Senior Security Engineer within the Security Engineering Team provides in-depth knowledge and skill in their areas of expertise. This includes 3rd line engineering tasks required to maintain, develop, and build the technology the team is responsible for, contributing to and making design decisions, involvement in projects, particularly where the delivery is complex, identifying and guiding the implementation of internal tasks to further evolve the capability and maturity of the team’s services.


Senior Security Engineers will be the first to engage with innovative technology, develop relevant processes and standards of operation. Through this they will also be an escalation point and mentor to more junior members of the team. Also providing ad-hoc consultancy outside of the team on specific, related requirements.


Key Responsibilities:

  • Common operational changes to technical security policies. This will include but is not limited to changes in Intrusion Prevention Systems, Proxies, End Point Detect and Response, Network Access Controls and Data Loss Prevention systems
  • Changes originate from projects requirements, response to security investigations, vendor upgrades or recommendations and general improvements.
  • Developing and deploying new configuration rules in relation to Security Monitoring Systems. This may include SIEM (Security Information and Event Management) log parsing, security event correlation rules and response playbook configuration
  • Developing, deploying, and maintaining integration and automation code in relation to security tools managed by the Security Engineering Team. This may include developments for other security teams as required
  • Emergency On call for Security Engineering supported technology. Providing engineering triage and resolution.
  • 3rd line engineering support in relation to the continued operational resilience of Security Engineering managed systems. Issues being escalated by 1st or 2nd line operational health processes. Leading post incident reviews to identify areas where future issues may be prevented
  • Support other team members in planning and implementation of Security Engineering managed system upgrades and new deployments. Liaising with vendor and internal support teams to plan and implement required steps
  • Support regulatory audits, providing process and technology walk throughs, evidence and required reporting. Audits cover regulations and standard including Sarbanes Oxley, Payment Card Industry, Telecoms Security Act, ISO 27001, and others.


What We Need from You:

  • Strong background in common operating systems, Windows Server, Linux (Red Hat dominant)
  • Expert skill in tools and methods used in network troubleshooting, using them effectively to diagnose issues and identify solutions
  • Strong skill in scripting and coding methods with specific experience in at least one common language like Bash, Python, PowerShell
  • Problem solving mind set, able to demonstrate the ability to break down complex issues, communicate technical issues to colleagues and work collaboratively to reach a solution
  • Strong understanding of policy driven security technology. Able to demonstrate strong understanding of at least one perimeter or end point protection system
  • Experience in at least one Security Incident & Event Monitoring solution like ArcSight, Splunk, Azure Sentinel or Google Chronicle




We’ll be sending you emails about the status of your application. To make sure you receive these, please add and to your Safe Senders list.


We’re looking to pay a great compensation package (depending on experience) for this position. We also offer plenty of extras to sweeten the deal, which could include things like bonuses, life assurance cover, health care and lots of flexible benefits.  


Also, every employee has their personal development supported with a LinkedIn learning account; plus other role specific learning available through our award-winning digital learning platform - O2 Campus. 


We also believe a great work-life balance is important, so we’re open to considering flexible working arrangements. Like to know more, feel free to raise it.  


Join us and we’ll encourage you to be bold every day. So take a deep breath, your career is about to go to exciting new places. 


If you have any questions around the role then please email who will be happy to help.