From Colocation to Exfiltration: Practical Cache Side-Channel Attacks in the Modern Public Cloud

Sharing resources among tenants is fundamental to public clouds, enhancing efficiency but also creating opportunities for microarchitectural side-channel attacks. However, cloud vendors remain skeptical about the practicality of these attacks, particularly regarding the ability to co-locate attacker and victm, and to overcome system noise. In this work, we develop a series of techniques for each step of the attack and, for the first time, demonstrate cross-tenant information leakage on the public Google Cloud Run, refuting the belief that such attacks are impractical. Our findings highlight the need to secure public clouds against side-channel attacks.