Network Security Engineer

The ONE Group Ltd; Stevenage; On-site; GBP 42,000 - 64,000; Part time

Benefits offered by this job

Company bonus scheme

Pension contributions up to 14%

Paid overtime opportunities

Flexi-leave (up to 15 additional days)

Enhanced parental leave

Subsidised meals

Free parking

Excellent on-site facilities

Job summary

A leading security firm in Stevenage seeks a Network Security Engineer to protect critical infrastructure in a 24/7 Incident Response role. The ideal candidate will have experience with enterprise firewalls and network monitoring tools, alongside a strong understanding of TCP/IP and advanced firewall technologies. This role offers competitive compensation, pension contributions, and additional perks.

Qualifications

• Strong understanding of core networking principles.
• Hands-on experience with advanced firewall features.
• In-depth knowledge of cryptographic technologies.
• Experience with traffic analysis and threat detection.
• Understanding of secure network architectures.
• SC eligibility required with British citizenship.

Responsibilities

• Monitor and triage security events in a 24/7 SOC.
• Configure and maintain enterprise-level firewalls.
• Lead analysis to identify malicious network traffic.
• Implement secure changes to network architecture.
• Collaborate with teams for resilient network solutions.
• Support improvement of tooling and hardening recommendations.
• Collaborate with infrastructure, security and architecture teams.

Skills

TCP/IP

DNS

routing

switching

VLANs

load balancing

next-generation firewall technologies

network monitoring tools

OSI model

Tools

Cisco

Palo Alto

Checkpoint

PRTG

Nagios

Splunk

LogRhythm

Darktrace

Job description

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This range is provided by The ONE Group Ltd. Your actual pay will be based on your skills and experience — talk with your recruiter to learn more.

Base pay range

Direct message the job poster from The ONE Group Ltd

Working Pattern: 24/7 shift rota on-site & on-call

We’re looking for a Network Security Engineer to join a high-performance security operations environment, protecting critical infrastructure and ensuring the resilience of complex enterprise networks. You’ll work within a 24/7 Incident Response function, combining hands‑on engineering with real‑time threat detection, investigation, and remediation.

Key Responsibilities:

• Monitor, investigate and triage security events within a 24/7 SOC environment
• Configure, maintain and troubleshoot enterprise firewalls (Cisco, Palo Alto, Checkpoint)
• Manage secure proxy platforms such as Bluecoat or F5, including content filtering and SSL inspection
• Lead deep-dive analysis using packet capture to identify malicious traffic and attacker behaviours
• Implement secure changes across network architecture, ensuring compliance and best practices
• Support continuous improvement through the optimisation of network security tools, including “purple team” feedback and hardening recommendations
• Contribute to the standardisation of network security tooling and documentation
• Collaborate with infrastructure, security and architecture teams to deliver robust, resilient network solutions

About You:

• Strong understanding of core networking: TCP/IP, DNS, routing, switching, VLANs, load balancing
• Hands‑on experience with next‑generation firewall technologies and advanced features (IPS/IDS, SSL decryption, DPI)
• In‑depth knowledge of IPSec, SSL/TLS, VPNs and authentication mechanisms
• Experience with network monitoring tools (PRTG, Nagios or similar)
• Ability to analyse complex traffic flows and identify threat patterns such as exploitation, C2, lateral movement, or exfiltration
• Understanding of secure network architectures (DMZs, segmentation, internal zones)
• Exposure to SIEM platforms (Splunk, LogRhythm, Darktrace) is beneficial
• Experience interpreting OSI model behaviours and protocol‑level diagnostics is advantageous
• SC eligible with British citizenship
• Company bonus scheme
• Pension contributions up to 14%
• Paid overtime opportunities
• Flexi‑leave (up to 15 additional days)
• Enhanced parental leave
• Subsidised meals, free parking and excellent on‑site facilities

Seniority level

• Mid‑Senior level

Employment type

• Part‑time

Job function

• Information Technology, Production, and Analyst

Industries

• Aviation and Aerospace Component Manufacturing
• Defense and Space Manufacturing

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