DDIO, or Direct Data I/O, is an Intel-exclusive performance enhancement that allows NICs to directly access a processor's L3 cache, completely bypassing the a server's RAM, to increase NIC performance and lower latencies. Cybersecurity researchers from the Vrije Universiteit Amsterdam and ETH Zurich, in a research paper published on Tuesday, have discovered a critical vulnerability with DDIO that allows compromised servers in a network to steal data from every other machine on its local network. This include the ability to obtain keystrokes and other sensitive data flowing through the memory of vulnerable servers. This effect is compounded in data centers that have not just DDIO, but also RDMA (remote direct memory access) enabled, in which a single server can compromise an entire network. RDMA is a key ingredient in shoring up performance in HPCs and supercomputing environments. Intel in its initial response asked customers to disable DDIO and RDMA on machines with access to untrusted networks, while it works on patches.

The NetCAT vulnerability spells big trouble for web hosting providers. If a hacker leases a server in a data-center with RDMA and DDIO enabled, they can compromise other customers' servers and steal their data. "While NetCAT is powerful even with only minimal assumptions, we believe that we have merely scratched the surface of possibilities for network-based cache attacks, and we expect similar attacks based on NetCAT in the future," the paper reads. We hope that our efforts caution processor vendors against exposing microarchitectural elements to peripherals without a thorough security design to prevent abuse." The team also published a video briefing the nature of NetCAT. AMD EPYC processors don't support DDIO.