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) Looking for members to join our mobile phone business “They cannot succeed if they step into the field at this late date” Some people say Rakuten is reckless in trying to enter the mobile communications business. However, innovation is realized if we succeed when something seems impossible. At Rakuten, we think the world changes when we achieve such changes. Because our history has always been a series of innovations since our establishment. Launching a communication carrier is an opportunity that we have once in our lives. Crack open the current communication industry. Blow new wind into life. Why not create innovation with us? Why not do something big? Job Opening: Regular Employee Company Name Rakuten Mobile, Inc. Qualifications [Required] TOEIC score of 600 or equivalent English proficiency/skills. Rakuten Group Englishnization Rakuten Mobile, Inc. aims for all employees to achieve a TOEIC score of 800 or higher, in line with Rakuten Group, Inc.'s Englishnization policy. As a first step, a TOEIC score of 600 (or equivalent English proficiency) is required for mid-career hires. Job Responsibilities [Upon initial hiring] Varies depending on the position. The scope of work changes may include assignments to other duties determined by the company based on directives, etc. (If a transfer is ordered in accordance with the secondment regulations, the duties will be those of the seconded company.) Contract Period No fixed term Probationary Period Yes (3 months) The probationary period may be extended at the company's discretion. Employment conditions will not change during the probationary period. Work Location [Upon initial hiring] Headquarters (Rakuten Crimson House, 1-14-1 Tamagawa, Setagaya-ku, Tokyo), and other business sites. The scope of work location changes may include reassignments or transfers to locations nationwide and overseas. If remote work is partially permitted, the work location will be the remote work location approved by the company. The work location at the time of hiring will be communicated in the job description for each position and the offer letter. As a measure against passive smoking, smoking is prohibited on the premises of Rakuten Crimson House (however, this may vary depending on the business site). Working Hours Standard working hours: 9:00 AM - 5:30 PM On days when Rakuten Group morning meetings are held, the prescribed working hours will be 8:00 AM - 4:30 PM. Prescribed working hours are 7.5 hours, with a 1-hour break. A flextime system is partially applied. Core time: 11:00 AM - 3:00 PM (8:00 AM - 12:00 PM on morning meeting days) Some positions may differ from the above; details will be specified in the offer letter (e.g., application of discretionary labor system). Overtime work or work on holidays may be instructed. Holidays/Leave/Absence Complete two-day weekend system (Saturday and Sunday) and national holidays Summer vacation, New Year's holiday, annual paid leave, menstrual leave, special leave (condolence, volunteer, etc.) Maternity leave, childcare leave, family care leave Some positions may differ from the above; details will be specified in the offer letter. Salary Monthly salary: JPY300,000 ~ (Breakdown: Base salary JPY 227,848 + fixed overtime pay for 40 hours JPY 72,152) The above is the minimum salary offered for mid-career hires. Overtime work exceeding 40 hours per month will be paid separately as overtime allowance. Some positions may differ from the above; details will be specified in the offer letter (e.g., application of discretionary labor system). Commuting allowance will be provided (conditions and maximum amount apply). Salary Increase Yes Reviewed in January and July based on company performance and individual evaluation. Bonus Yes Paid in June and December based on company performance and individual evaluation. Stock Option Plan Yes Retirement Allowance Yes Insurance Employees' Pension Insurance, Health Insurance, Workers' Accident Compensation Insurance, Employment Insurance, etc. Benefits Cafeteria (breakfast, lunch, dinner generally free) Employee Stock Ownership Plan English learning support, etc. Job Opening: Fixed-term Employee Company Name Rakuten Mobile, Inc. Qualifications Varies depending on the recruiting position. Job Responsibilities [Upon initial hiring] Varies depending on the recruiting position. The scope of work changes may include assignments to other duties determined by the company based on directives, etc. (If a transfer is ordered in accordance with the secondment regulations, the duties will be those of the seconded company.) Contract Period Fixed term Maximum contract renewal period: Yes (The total contract period is 5 years, starting from the initial employment contract date.) Probationary Period None Work Location [Upon initial hiring] Headquarters (Rakuten Crimson House, 1-14-1 Tamagawa, Setagaya-ku, Tokyo), and other business sites. The scope of work location changes may include reassignments or transfers to locations nationwide and overseas. If remote work is partially permitted, the work location will be the remote work location approved by the company. The work location at the time of hiring will be communicated in the job description for each position and the offer letter. As a measure against passive smoking, smoking is prohibited on the premises of Rakuten Crimson House (however, this may vary depending on the business site). Working Hours Standard working hours: 9:00 AM - 5:30 PM On days when Rakuten Group morning meetings are held, the prescribed working hours will be 8:00 AM - 4:30 PM. Prescribed working hours are 7.5 hours, with a 1-hour break. A flextime system is partially applied. Core time: 11:00 AM - 3:00 PM (8:00 AM - 12:00 PM on morning meeting days) Some positions may differ from the above; details will be specified in the offer letter (e.g., application of discretionary labor system). Overtime work or work on holidays may be instructed. Holidays/Leave/Absence Complete two-day weekend system (Saturday and Sunday) and national holidays Summer vacation, New Year's holiday, annual paid leave, menstrual leave, special leave (condolence, volunteer, etc.) Maternity leave, childcare leave, family care leave Some positions may differ from the above; details will be specified in the offer letter. Salary Determined individually based on experience, etc. Commuting allowance will be provided (conditions and maximum amount apply). Salary Increase Yes Upon contract renewal, a salary revision may be proposed based on the most recent evaluation. Bonus May be paid taking into account company performance, general economic conditions, and work performance/abilities. Stock Option Plan None Retirement Allowance None Insurance Employees' Pension Insurance, Health Insurance, Workers' Accident Compensation Insurance, Employment Insurance, etc. Benefits Cafeteria (breakfast, lunch, dinner generally free) Employee Stock Ownership Plan English learning support, etc.

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