We’re hiring! Aon is seeking a Senior Network Security Consultant to join our Digital M&A Advisory practice in London.

The team advises private equity investors, infrastructure funds and corporate clients on technology, IT, cyber and digital risks across acquisitions, portfolio companies and strategic transformation initiatives. Our work spans cyber due diligence, technical cyber reviews, cyber risk assessments, network and infrastructure security reviews, separation and integration support, and post-transaction cyber value creation.

This role is ideally suited to a technically strong network specialist with hands-on experience designing, implementing or assessing enterprise network architectures, segmentation and firewall configurations across on-premise, cloud and hybrid environments. Previous M&A experience is not required. You will act as the technical network security lead on our engagements, working directly with investors, CISOs, infrastructure and network teams and C-suite executives to assess network security posture, identify exposures and translate technical findings into clear business and investment implications. This is a fast-paced, client-facing role offering significant exposure to a broad range of industries, network environments and technologies.

About Aon

Headquartered in London, Aon Plc is a leading global professional services firm providing a broad range of risk, retirement and health solutions. Our 50,000 colleagues in 120 countries empower results for clients by using proprietary data and analytics to deliver insights that reduce volatility and improve performance. Aon is an equal opportunities employer. Aon's recruitment and selection policy ensures the best possible skill mix of colleagues and the highest quality candidates are appointed using objective job-related criteria.

About the Role

Your impact as a Senior Network Security Consultant:

YouYou will be responsible for leading the network security elements of engagements across private equity and corporate clients, including:

• Leading technical network security reviews as part of cyber due diligence, technical reviews and portfolio company engagements.

• Assessing enterprise network architecture and design across data centres, offices, sites, cloud and hybrid environments, including WAN, LAN, SD-WAN and remote access.

• Reviewing network segmentation and zoning, including VLANs, VRFs, DMZs, micro-segmentation and separation of critical, production and user environments.

• Reviewing firewall configurations and rule bases (e.g. Palo Alto, Fortinet, Check Point, Cisco), identifying overly permissive, redundant or shadowed rules, insecure services and gaps in change control.

• Assessing perimeter and internet exposure, including externally facing services, VPN and remote access gateways, web application firewalls and DDoS protection.

• Evaluating cloud network security controls across Azure and AWS, including VNets/VPCs, security groups, NSGs, private endpoints and hybrid connectivity (ExpressRoute, Direct Connect, site-to-site VPN).

• Assessing IT/OT network separation and industrial network security (e.g. Purdue model, IEC 62443) where relevant.

• Reviewing network access control, Zero Trust Network Access (ZTNA) and SASE/SSE architectures.

• Assessing network monitoring, logging and detection capabilities, including NDR, IDS/IPS, NetFlow and integration with SOC/SIEM services.

• Reviewing the hardening, patching and lifecycle status of network devices, including end-of-life infrastructure.

• Translating technical findings into prioritised, commercially relevant risks, remediation roadmaps and cost estimates for investors and management teams.

• Producing high-quality reports, presentations and executive briefings.

• Managing technical workstreams and supporting engagement delivery across multiple concurrent projects.

• Working closely with colleagues across technology, cyber, M&A and risk advisory disciplines.

• Contributing to the development of the team's technical review methodologies, network assessment tooling and market offerings.

• Supporting client engagements across the UK and EMEA.

About you

Your knowledge and expertise:

Technical

• Demonstrable experience in network engineering, network security, network architecture, security consulting or a related technical role.

• Strong, hands-on experience implementing and assessing network segmentation and firewall configurations in complex enterprise environments.

• Experience designing, implementing or assessing one or more of the following:

  • Network segmentation and zoning (VLANs, VRFs, DMZs, micro-segmentation)
  • Next-generation firewalls and rule base management (Palo Alto, Fortinet, Check Point, Cisco)
  • Routing and switching (e.g. BGP, OSPF) and enterprise LAN/WAN/SD-WAN
  • VPN, remote access, ZTNA and SASE/SSE solutions
  • Cloud networking and security in Azure and/or AWS
  • Network access control (802.1X, NAC)
  • IDS/IPS, NDR and network monitoring
  • Wireless network security
  • OT and industrial network security
  • Network resilience, redundancy and disaster recovery

• Familiarity with one or more of the following frameworks and best practices:

  • CIS Benchmarks and CIS Critical Security Controls
  • NIST CSF and NIST SP 800-41 (firewall guidance)
  • NIST SP 800-207 (Zero Trust Architecture)
  • ISO 27001
  • IEC 62443 and the Purdue model

• Understanding of common network attack techniques (e.g. lateral movement, exploitation of exposed services, misconfigured trust relationships) and how they impact critical business assets.

• Ability to interpret firewall rule bases, device configurations, network diagrams and outputs.

• Experience identifying and assessing network and cyber risks within complex environments, with the ability to communicate technical findings and business implications to both technical and non-technical stakeholders.

• Strong analytical and problem-solving skills.

• Commercial awareness and the ability to understand business implications of technology and security decisions.

• Excellent written and verbal communication skills with the ability to convey complex technical concepts to non-technical audiences.

Team & Client Management

• Experience managing technical workstreams and contributing to successful project delivery.

• Strong stakeholder management and presentation skills.

• Ability to engage effectively with both technical teams and senior business executives.

• Experience developing positive client relationships.

• Comfortable working within multidisciplinary and global teams and fast-paced consulting environments.

• Ability to manage multiple engagements and competing priorities.

• Highly organised with strong attention to detail and quality.

Highly Desirable

• Experience in OT/ICS environments, such as manufacturing, energy, utilities or infrastructure.

• Exposure to attack path analysis, exposure management or cyber risk quantification platforms.

• Experience of network penetration testing, firewall audits or security assurance reviews.

• Experience supporting network separations, integrations, data centre migrations or infrastructure modernisation programmes.

• Industry-recognised certifications, such as:

  • Cisco CCNP / CCIE (Enterprise or Security)
  • Palo Alto PCNSE
  • Fortinet NSE 7 / FCSS
  • Check Point CCSE
  • GIAC GCIA or GICSP
  • CISSP

• Experience working with private equity-backed businesses or large corporate organisations.

• Experience mentoring junior team members or supporting team development initiatives.

• Interest in supporting client relationship management.

What Success Looks Like

• Delivering high-quality, technically robust network security reviews for private equity and corporate clients.

• Acting as the go-to network security expert across engagements.

• Building trusted relationships with client technology, security and business stakeholders.

• Providing insightful, commercially relevant recommendations that support investment and operational decision-making.

• Contributing to the growth and development of the Digital M&A Advisory practice and its technical capabilities.

• Supporting the development of junior colleagues and enhancing team capabilities.

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