Network Engineer

Senior Network Engineer – Firewall Remediation 6-Month FTC + Potential Extension | Sheffield / Hybrid

I'm working with a large, complex multi‑site organisation currently undertaking a major network security and firewall remediation programme.

Following a wider review of the network security estate, they're looking for an experienced Senior Network Security Engineer to take ownership of a hands‑on remediation workstream across their enterprise firewall environment.

This isn't a traditional BAU support role. You'll be working through an existing firewall estate, reviewing security policies and access rules, understanding legitimate network and application traffic, and implementing the technical changes required to strengthen the environment.

You’ll work closely with Network, Infrastructure, Security and Application teams to review and improve the organisation's existing firewall policies.

The work will include:

• Reviewing existing firewall rules, policies and access controls.
• Analysing network and application traffic to understand legitimate communication requirements.
• Identifying redundant, outdated or overly permissive firewall rules.
• Implementing firewall policy changes and security remediation.
• Hands‑on configuration and administration of Cisco Firepower, FTD and FMC
  .
• Reviewing NAT, access rules and wider firewall security policies.
• Improving network segmentation and reducing unnecessary network access.
• Supporting IPS/IDS, logging and network security visibility.
• Working with application and infrastructure teams to understand system dependencies.
• Planning and delivering technical changes through structured change‑control processes.
• Producing implementation plans, technical documentation and rollback procedures.
• Carrying out pre and post‑change validation.
• Supporting technical reviews and providing clear updates on remediation progress.

You’ll need strong hands‑on experience working within enterprise network security and firewall environments.

Ideally, you’ll have experience across:

• Enterprise firewall policy and rule management.
• Firewall rule reviews, audits or remediation.
• Network traffic analysis and troubleshooting.
• NAT and access‑control policies.
• Security policy implementation.
• Change control and rollback planning.

Experience with technologies such as Cisco ISE, Palo Alto, Fortinet, Check Point, Wireshark or SIEM platforms would also be highly relevant.

They're particularly interested in engineers who have worked on network security transformation, firewall remediation, security hardening, post‑incident improvement or large‑scale infrastructure security programmes
.

This is a highly technical, hands‑on role where you’ll have a genuine impact on the security of a large enterprise network.

The initial programme is expected to run for six months
, with the potential for extension as the wider network security programme develops.

The organisation can be flexible around hybrid working for the right technical profile
, although some initial on‑site presence in Sheffield will be required to understand the environment and key stakeholders.

Salary is flexible depending on experience.