Security engineer

Refractal is an AI security company building the infrastructure organisations need to defend against autonomous AI threats. 2026 has shown that generally capable intelligence is here. The challenge now is modernising security to stop AI-enabled threats, whether they come from internal agents going rogue or from attackers using AI to become more dangerous.

• Design and execute assessments of AI applications and agents, grounded in realistic attacker goals and clearly defined test scope.
• Test realistic threats such as indirect prompt injection, misuse of connected tools, sensitive data exposure and attempts to cross permission boundaries.
• Build reproducible test cases and small testing tools that demonstrate security impact and distinguish reliable failures from one-off outputs.
• Analyse how model behaviour, application design, identity and permissions combine to create vulnerabilities.
• Document findings, recommend practical mitigations and retest fixes with the engineers responsible for the affected systems.

• Hands-on experience in offensive security, application security testing or adversarial testing of AI systems.
• A solid understanding of web applications, APIs, authentication, authorisation and common security failure modes.
• An understanding of how AI applications use prompts, retrieved information, memory and connected tools, and where trust boundaries arise.
• The ability to write code that automates testing, reproduces findings and inspects application behaviour.
• Good judgement around test scope and sensitive data, and the ability to explain technical findings in terms of practical impact.
• Будет плюсом: Experience assessing LLM applications, agent workflows or systems that retrieve external content; Experience building security evaluation suites or testing proposed mitigations systematically; Experience combining application testing with cloud, identity or infrastructure security assessment

• Salary: £65,000–£125,000
• Competitive equity to share in Refractal's growth
• Pension contribution
• Private medical and dental cover
• Visa and relocation support