Network Security Engineer

The ONE Group Ltd

Stevenage

On-site

GBP 42,000 - 64,000

Part time

14 days+

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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

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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