Researchers have disclosed a new hardware attack, called DDRop, that breaks the memory protection in Intel and AMD confidential computing by silently dropping writes to a server’s memory, so the processor keeps reading old encrypted data as if it were current.

The attack requires an attacker who already controls the server’s software and can briefly access the machine to insert a small circuit board, called an interposer, between the processor and a memory module.

The interposer costs under $200 to build. DDRop works against Intel TDX, Intel Scalable SGX, and AMD SEV-SNP, the hardware that cloud services use to keep customer data private while it is in use, even from the cloud provider.