Senior Penetration Tester - Security Assurance Section (RMI Telecommunication Security Supervisory Dep)
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Before you apply
LocationTokyo, Japan; Osaka, Japan
SenioritySenior
Experience10+ yrs
Company size10,000+ people
PostedSep 23, 2026 · 1mo ago
Verified live1d ago
At a glanceSummarised by Seekless from the posting.
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)
Experience with telecom technologies, mobile core networks, BSS/OSS systems, and cloud-native telecom applications
OSCP, CRTP, CRTO, OSEP, OSWE, GPEN, GXPN, or equivalent
AI/LLM security testing and adversarial machine learning
Red team operations and advanced exploit development
Bug bounty, vulnerability research, and AI-assisted penetration testing
Skills
Burp Suite
Kali Linux
Metasploit
BloodHound
Nmap
Nessus
Python
JavaScript
Bash
PowerShell
AWS
Azure
GCP
Kubernetes
Docker
Job Description:
About Organization
At Rakuten Mobile Security Assurance, you will help secure one of the world’s most advanced cloud-native telecom networks, protecting millions of customers across digital, mobile, cloud, and AI-driven services. We work on cutting-edge offensive security challenges spanning 4G/5G telecom platforms, cloud-native infrastructure, APIs, AI/ML systems, and emerging technologies.
We offer an environment where innovation is encouraged, continuous learning is supported, and security experts are empowered to make a direct business impact. You will work alongside industry-leading engineers, build next-generation security capabilities, leverage AI to transform security testing, and contribute to protecting critical telecommunications infrastructure at scale.
Job Duties
•
Comprehensive Penetration Testing: Conduct manual and automated testing of web/mobile applications, APIs, cloud platforms, and network infrastructure.
•
AI/ML Security Assessments: Evaluate LLM-based systems, AI agents, RAG implementations, and MLOps pipelines. Identify vulnerabilities such as prompt injection, insecure model integrations, data leakage, and AI supply chain risks.
•
Telecom Security Testing: Execute security assessments on telecom-specific systems, including BSS/OSS applications, eSIM platforms, subscriber management, and mobile network services.
•
Red Teaming & Adversary Emulation: Support red team exercises, conduct attack path analysis, and perform exploit validation using realistic attacker techniques.
•
Design & Code Review: Perform source code reviews, secure design reviews, and architecture-level security assessments.
•
Reporting & Remediation: Develop proof-of-concepts, create detailed technical reports, and provide actionable remediation recommendations. Validate fixes through re-testing.
•
Research & Innovation: Research emerging attack techniques, exploit methodologies, and AI-assisted offensive security methods.
Minimum Qualifications
•
Experience: 10+ years of hands-on penetration testing and application security experience.
•
Technical Expertise: Deep expertise in web, mobile, API, cloud, infrastructure, and AI security testing.
•
Tooling: Proficiency with Burp Suite, Kali Linux, Metasploit, BloodHound, Nmap, Nessus, and modern offensive security frameworks.
•
Scripting/Coding: Strong knowledge of Python, JavaScript, Bash, or PowerShell for testing and automation.
•
Cloud/Infrastructure: Proficiency with cloud platforms (AWS, Azure, or GCP) and containerized environments (Kubernetes, Docker).
Preferred Qualifications
•
Telecom Expertise: Experience with telecom technologies, mobile core networks, BSS/OSS systems, and cloud-native telecom applications.
•
Certifications: OSCP, CRTP, CRTO, OSEP, OSWE, GPEN, GXPN, or equivalent.
•
Specialized Skills:
•
AI/LLM security testing and adversarial machine learning.
•
Red team operations and advanced exploit development.
•
Bug bounty, vulnerability research, and AI-assisted penetration testing.
Languages:
English (Overall - 3 - Advanced)
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