Senior Penetration Tester

Appealing Points

• Work on cutting-edge offensive security across 4G/5G telecom platforms, cloud-native infrastructure, APIs, and AI/ML systems
• Direct exposure to AI/LLM security testing, red teaming, and adversarial machine learning on large-scale critical infrastructure
• Collaborative environment with industry-leading engineers, strong support for continuous learning, and the chance to build next-generation security capabilities

Annual Salary: ¥10,000,000 and above

Job Description

This Security Assurance team works to secure one of the world's most advanced cloud-native telecom networks, protecting millions of customers across digital, mobile, cloud, and AI-driven services. The team tackles offensive security challenges spanning 4G/5G telecom platforms, cloud-native infrastructure, APIs, AI/ML systems, and emerging technologies, in an environment that encourages innovation, continuous learning, and direct business impact.

Job Responsibilities

• Conduct manual and automated penetration testing of web/mobile applications, APIs, cloud platforms, and network infrastructure
• Evaluate LLM-based systems, AI agents, RAG implementations, and MLOps pipelines for vulnerabilities such as prompt injection, insecure model integrations, data leakage, and AI supply chain risks
• Execute security assessments on telecom-specific systems, including BSS/OSS applications, eSIM platforms, subscriber management, and mobile network services
• Support red team exercises, conduct attack path analysis, and perform exploit validation using realistic attacker techniques
• Perform source code reviews, secure design reviews, and architecture-level security assessments
• Develop proof-of-concepts, create detailed technical reports, provide actionable remediation recommendations, and validate fixes through re-testing
• Research emerging attack techniques, exploit methodologies, and AI-assisted offensive security methods

Required Qualifications

• 10+ years of hands-on penetration testing and application security experience
• Deep expertise in web, mobile, API, cloud, infrastructure, and AI security testing
• Proficiency with Burp Suite, Kali Linux, Metasploit, BloodHound, Nmap, Nessus, and modern offensive security frameworks
• Strong knowledge of Python, JavaScript, Bash, or PowerShell for testing and automation
• Proficiency with cloud platforms (AWS, Azure, or GCP) and containerized environments (Kubernetes, Docker)

Preferred Qualifications

• Experience with telecom technologies, mobile core networks, BSS/OSS systems, and cloud-native telecom applications
• Certifications such as OSCP, CRTP, CRTO, OSEP, OSWE, GPEN, GXPN, or equivalent
• Specialized skills in AI/LLM security testing and adversarial machine learning; red team operations and advanced exploit development; bug bounty, vulnerability research, and AI-assisted penetration testing

Language Requirements: Advanced Business level English

About Company:

The largest eCommerce company in Japan, and the third-largest eCommerce marketplace company worldwide. The organization provides a variety of consumer and business-focused services including e-commerce, e-reading, travel, banking, securities, credit card, e-money, portal and media, online marketing, and professional sports. The company is expanding globally and currently has operations throughout Asia, Western Europe, and the Americas.

[Measures against passive smoking]

No smoking indoors allowed

Designated smoking area

. Skillset Required: offensive security, 4G, 5G, telecom platforms, cloud-native infrastructure, APIs, AI/ML systems, AI security testing, red teaming, adversarial machine learning, penetration testing, application security, web security testing, mobile security testing, API security testing, cloud security testing, infrastructure security testing, Burp Suite, Kali Linux, Metasploit, BloodHound, Nmap, Nessus, offensive security frameworks, Python, JavaScript, Bash, PowerShell, testing automation, AWS, Azure, GCP, containerized environments, Kubernetes, Docker, telecom technologies, mobile core networks, BSS/OSS systems, cloud-native telecom applications, OSCP, CRTP, CRTO, OSEP, OSWE, GPEN, GXPN, AI/LLM security testing, adversarial machine learning, red team operations, advanced exploit development, bug bounty, vulnerability research, AI-assisted penetration testing, manual penetration testing, automated penetration testing, security assessments, attack path analysis, exploit validation, source code review, secure design review, architecture security assessments, proof-of-concept development, technical report writing, remediation recommendations, re-testing, emerging attack techniques, exploit methodologies, AI-assisted offensive security