General

Meltdown and Spectre FAQ: How the critical CPU flaws affect PCs and Macs

Massive security vulnerabilities in modern CPUs are forcing a redesign of the kernel software at the heart of all major operating systems. Since the issues—dubbed Meltdown and Spectre—exist in the CPU hardware itself, Windows, Linux, Android, macOS, iOS, Chromebooks, and other operating systems all need to protect against it. And worse, plugging the hole can negatively affect your PC’s performance.

Everyday home users shouldn’t panic too much though. Just apply all available updates and keep your antivirus software vigilant, as ever. If you want to dive right into the action without all the background information, we’ve also created a focused guide on how to protect your PC against Meltdown and Spectre.

Here’s a high-level look at what you need to know about Meltdown and Spectre, in plain language. Be sure to read Google’s post on the CPU vulnerabilities if you like diving deep into technical details.  

Meltdown and Spectre CPU flaw FAQ

Editor’s note: This article was most recently updated to to include Intel metrics on how the Windows patches affect PC performance in best-case scenarios, more details on how Intel plans to issue CPU firmware updates, and to link to a list of affected Chromebooks in the available patches section.

Give it to me straight—what’s the issue here?

Again, the CPU exploits in play here are extremely technical, but in a nutshell, the exploit allows access to your operating system’s sacrosanct kernel memory because of how the processors handle “speculative execution,” which modern chips perform to increase performance. An attacker can exploit these CPU vulnerabilities to expose extremely sensitive data in the protected kernel memory, including passwords, cryptographic keys, personal photos, emails, or any other data on your PC.

Meltdown is the more serious exploit, and the one that operating systems are rushing to fix. It “breaks the most fundamental isolation between user applications and the operating system,” according to Google. This flaw most strongly affects Intel processors because of the aggressive way they handle speculative execution, though a few ARM cores are also susceptible.

Core i7-8700K Coffee Lake Gordon Mah Ung

Even new Intel chips like the Core i7-8700K are affected by Meltdown and Spectre.

Spectre affects AMD and ARM processors as well as Intel CPUs, which means mobile devices are also at risk. (We have a separate FAQ on how Spectre affects phones and tablets.) There may be no hardware solution to Spectre, which “tricks other applications into accessing arbitrary locations in their memory.” Software needs to be hardened to guard against it. 

What’s a kernel?

The kernel inside your operating system is basically an invisible process that facilitates the way apps and functions work on your computer, talking directly to the hardware. It has complete access to your operating system, with the highest possible level of permissions. Standard software has much more limited access. Here’s how The Register puts it: “Think of the kernel as God sitting on a cloud, looking down on Earth. It’s there, and no normal being can see it, yet they can pray to it.”

How do I know if my PC is at risk?

Short answer: It is. Yes, even if it’s a Mac.