The Effects of the Spectre and Meltdown Vulnerabilities

On January 3, the world learned about a series of major security vulnerabilities in modern microprocessors. Called Spectre and Meltdown, these vulnerabilities were discovered by several different researchers last summer, disclosed to the microprocessors’ manufacturers, and patched­ — at least to the extent possible.

This news isn’t really any different from the usual endless stream of security vulnerabilities and patches, but it’s also a harbinger of the sorts of security problems we’re going to be seeing in the coming years. These are vulnerabilities in computer hardware, not software. They affect virtually all high-end microprocessors produced in the last 20 years. Patching them requires large-scale coordination across the industry, and in some cases drastically affects the performance of the computers. And sometimes patching isn’t possible; the vulnerability will remain until the computer is discarded.

Spectre and Meltdown aren’t anomalies. They represent a new area to look for vulnerabilities and a new avenue of attack. They’re the future of security­ — and it doesn’t look good for the defenders.

Modern computers do lots of things at the same time. Your computer and your phone simultaneously run several applications — ­or apps. Your browser has several windows open. A cloud computer runs applications for many different computers. All of those applications need to be isolated from each other. For security, one application isn’t supposed to be able to peek at what another one is doing, except in very controlled circumstances. Otherwise, a malicious advertisement on a website you’re visiting could eavesdrop on your banking details, or the cloud service purchased by some foreign intelligence organization could eavesdrop on every other cloud customer, and so on. The companies that write browsers, operating systems, and cloud infrastructure spend a lot of time making sure this isolation works.

Both Spectre and Meltdown break that isolation, deep down at the microprocessor level, by exploiting performance optimizations that have been implemented for the past decade or so. Basically, microprocessors have become so fast that they spend a lot of time waiting for data to move in and out of memory. To increase performance, these processors guess what data they’re going to receive and execute instructions based on that. If the guess turns out to be correct, it’s a performance win. If it’s wrong, the microprocessors throw away what they’ve done without losing any time. This feature is called speculative execution.

Spectre and Meltdown attack speculative execution in different ways. Meltdown is more of a conventional vulnerability; the designers of the speculative-execution process made a mistake, so they just needed to fix it. Spectre is worse; it’s a flaw in the very concept of speculative execution. There’s no way to patch that vulnerability; the chips need to be redesigned in such a way as to eliminate it.

Since the announcement, manufacturers have been rolling out patches to these vulnerabilities to the extent possible. Operating systems have been patched so that attackers can’t make use of the vulnerabilities. Web browsers have been patched. Chips have been patched. From the user’s perspective, these are routine fixes. But several aspects of these vulnerabilities illustrate the sorts of security problems we’re only going to be seeing more of.

First, attacks against hardware, as opposed to software, will become more common. Last fall, vulnerabilities were discovered in Intel’s Management Engine, a remote-administration feature on its microprocessors. Like Spectre and Meltdown, they affected how the chips operate. Looking for vulnerabilities on computer chips is new. Now that researchers know this is a fruitful area to explore, security researchers, foreign intelligence agencies, and criminals will be on the hunt.

Second, because microprocessors are fundamental parts of computers, patching requires coordination between many companies. Even when manufacturers like Intel and AMD can write a patch for a vulnerability, computer makers and application vendors still have to customize and push the patch out to the users. This makes it much harder to keep vulnerabilities secret while patches are being written. Spectre and Meltdown were announced prematurely because details were leaking and rumors were swirling. Situations like this give malicious actors more opportunity to attack systems before they’re guarded.

Third, these vulnerabilities will affect computers’ functionality. In some cases, the patches for Spectre and Meltdown result in significant reductions in speed. The press initially reported 30%, but that only seems true for certain servers running in the cloud. For your personal computer or phone, the performance hit from the patch is minimal. But as more vulnerabilities are discovered in hardware, patches will affect performance in noticeable ways.

And then there are the unpatchable vulnerabilities. For decades, the computer industry has kept things secure by finding vulnerabilities in fielded products and quickly patching them. Now there are cases where that doesn’t work. Sometimes it’s because computers are in cheap products that don’t have a patch mechanism, like many of the DVRs and webcams that are vulnerable to the Mirai (and other) botnets — ­groups of Internet-connected devices sabotaged for coordinated digital attacks. Sometimes it’s because a computer chip’s functionality is so core to a computer’s design that patching it effectively means turning the computer off. This, too, is becoming more common.

Increasingly, everything is a computer: not just your laptop and phone, but your car, your appliances, your medical devices, and global infrastructure. These computers are and always will be vulnerable, but Spectre and Meltdown represent a new class of vulnerability. Unpatchable vulnerabilities in the deepest recesses of the world’s computer hardware is the new normal. It’s going to leave us all much more vulnerable in the future.

This essay previously appeared on TheAtlantic.com.

Posted on January 26, 2018 at 6:12 AM • 57 Comments