Andreas Kleanthous, Deputy CISO at Rakuten Symphony Deutschland, joins us to share his global journey through cybersecurity; from red teaming and critical infrastructure protection to leading security innovation in cloud-native telecom and Open RAN.
1. Tell us about your journey to Rakuten Symphony.
My story begins on the beautiful island of Cyprus, nestled in the heart of the Mediterranean. Growing up there shaped my character; it instilled in me discipline, curiosity, and resilience. I moved to Greece for my undergraduate studies in Computer Science, which laid the technical foundation for my career. Driven by a growing interest in cybersecurity, I continued my academic path in the United States, where I earned a master’s degree in Cybersecurity and Digital Forensics.
This international exposure expanded not only my technical knowledge but also my understanding of global cyber threats and defense strategies. Joining Rakuten Symphony was a natural next step; the company’s mission at the intersection of cloud-native telecom and cybersecurity resonated with me. I was drawn to its commitment to innovation, openness, and embedding security at the core of next-generation network architecture.
2. What key experiences shaped your approach to cybersecurity, paving your way to becoming Deputy CISO here?
My approach to cybersecurity has been shaped by diverse and hands-on experiences across offensive security, critical infrastructure protection, and strategic cyber risk management.
Early in my career, I led a red teaming group focused on penetration testing and social engineering for financial institutions and other major organizations. These exercises taught me to think like an attacker and identify real-world vulnerabilities that are often overlooked.
A particularly formative role came when I oversaw cyber operations for the largest shipping company in Cyprus. Securing both IT and OT systems across a global fleet required a strategic balance of regulatory compliance, remote asset protection, and deep integration of cybersecurity into physical operations.
These cumulative experiences—from tactical offense to strategic defense—have given me a comprehensive understanding of cybersecurity. They also reinforced the importance of building a strong security culture across the organization, with resilient systems aligned to business goals. That is the mindset I bring to my role as Deputy CISO at Rakuten Symphony, especially as we secure our Open RAN infrastructure.
3. What are the unique security challenges you solve for Rakuten Symphony, which is in a highly dynamic telecom and cloud-native environment?
Rakuten Symphony operates in a dynamic environment that combines telecom with cloud-native technologies; each brings unique security challenges. One of our top priorities is securing the Open RAN architecture. Unlike traditional telecom systems, Open RAN uses disaggregated, multi-vendor components, which makes interoperability and interface protection essential. We ensure continuous monitoring, strong access controls, and policy enforcement to maintain security across these interconnected systems.
In our cloud-native environment, we focus on securing containers, microservices, and CI/CD pipelines. Security is embedded from the very start of the development lifecycle, not added as an afterthought.
A major turning point came when I assumed leadership of our Security Operations Center (SOC). At the time, it was underperforming and lacked clear processes. Through a full transformation: including new tools, streamlined workflows, and team upskilling, we turned the SOC into a proactive function that now plays a central role in our defense strategy. Our goal is simple; empower innovation through security, not hinder it.
4. What’s a recent security initiative or success that you’re particularly proud of?
The transformation of our Security Operations Center is a recent initiative I’m especially proud of. When I took over, the SOC had multiple gaps; it suffered from limited visibility, outdated processes, and unclear incident response plans. Over the past year, we launched a comprehensive improvement program to address these issues directly.
We redesigned the SOC’s structure, implemented a SOAR platform for automation, integrated real-time threat intelligence, and introduced playbooks aligned with regulatory standards. Most importantly, we invested in upskilling our team to face modern cyber threats.
Today, our SOC is a high-performing unit; it reduces alert fatigue, improves response times, and strengthens situational awareness across both telecom and cloud environments. It has become a reference point within Rakuten Symphony for operational excellence - a true testament to what leadership, collaboration, and vision can accomplish.
5. Outside of work, what do you enjoy doing that helps you recharge or stay inspired in this high-pressure role?
To stay balanced and focused in a high-pressure role, I prioritize physical and mental well-being. I train regularly through calisthenics and maintain a healthy lifestyle that keeps me energized and clear headed. The discipline gained through this practice directly supports my professional mindset.
I’m also a collector of Marvel and DC collectibles; this hobby connects me with creativity and storytelling, offering a welcome break from the technical demands of my work. It brings joy and reminds me to stay curious.
Travel is another outlet; I’ve visited 35 countries so far. Experiencing different cultures and perspectives often sparks new ideas and solutions that I bring back into my work. These interests help me recharge, stay grounded, and maintain a fresh perspective for every challenge.
6. What advice would you give to new joiners at Rakuten Symphony?
To new joiners, my advice is simple; be curious, collaborative, and proactive. We operate in a fast moving, innovation driven environment where agility and cross-functional teamwork are vital. Take the time to understand how your role contributes to the broader mission; particularly as we advance Open RAN and cloud native telecom.
Ask questions. Share ideas. Seek mentorship. This is a culture that values initiative and open communication; your contributions can make a real difference from day one. Be prepared to adapt and grow - change is constant in this industry, and adaptability is a key strength.
Finally, always keep security in mind. Regardless of your function - engineering, operations, or product - security is everyone’s responsibility. As Aristotle said: “The more you know, the more you realize you don’t know.” This is a reminder that true mastery begins with humility and that mindset is essential for thriving at Rakuten Symphony.
