Intel: You don’t need to disable Hyper-Threading to protect against the ZombieLoad CPU exploit – PCWorld

Intel: You don’t need to disable Hyper-Threading to protect against the ZombieLoad CPU exploit – PCWorld

If you’re in a panic to figure out how to turn off Intel’s Hyper-Threading feature to prevent ZombieLoad, the latest Spectre-like CPU security exploit, then take a deep breath: Intel’s official guidance does not actually recommend that. The bad news? None of what we tell you is going to make you feel any better.

ZombieLoad is similar to previous “side channel” attacks, which trick Intel processors into coughing up potentially sensitive information that otherwise would be kept private by the CPU. The exploit hits most Intel chips and can be used on Windows, MacOS, and Linux, the ZombieLoad researchers said. ARM-based and AMD-based CPUs aren’t impacted.

“While programs normally only see their own data, a malicious program can exploit the fill buffers to get hold of secrets currently processed by other running programs,” the discoverers of the exploit said. “These secrets can be user-level secrets, such as browser history, website content, user keys, and passwords, or system-level secrets, such as disk encryption keys.”


The ZombieLoad logo.

Intel agreed with the exploit’s capabilities but downplayed the level of risk ZombieLoad imposed. Intel also decided to name the exploit Microarchitectural Data Sampling, or MDS. That’s a lot less scary-sounding. 

“MDS techniques are based on a sampling of data leaked from small structures within the CPU using a locally executed speculative execution side channel,” the company said. “Practical exploitation of MDS is a very complex undertaking. MDS does not, by itself, provide an attacker with a way to choose the data that is leaked.”

Intel said operating system, firmware, and hardware mitigations address many of the problems.

“Microarchitectural Data Sampling (MDS) is already addressed at the hardware level in many of our recent 8th and 9th Generation Intel Core processors, as well as the 2nd Generation Intel Xeon Scalable processor family,” the company said in a statement. “For other affected products, mitigation is available through microcode updates, coupled with corresponding updates to operating system and hypervisor software that are available starting today. We’ve provided more information on our website and continue to encourage everyone to keep their systems up to date, as it’s one of the best ways to stay protected.”

9th-gen Intel Core i9-9900K Gordon Mah Ung

Intel officials also went out of their way to point out that the ZombieLoad research team worked with it and others in the PC industry to put fixes in place before disclosing the exploit.

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