Details have emerged on two major processor security flaws this week, and the industry is scrambling to issue fixes and secure machines for customers. Dubbed “Meltdown” and “Spectre,” the flaws affect nearly every device made in the past 20 years. The Meltdown flaw primarily affects Intel and ARM processors, and researchers have already released proof-of-concept code that could lead to attacks using Meltdown.

The vulnerabilities allow an attacker to compromise the privileged memory of a processor by exploiting the way processes run in parallel. They also allow an attacker to use JavaScript code running in a browser to access memory in the attacker’s process. That memory content could contain key strokes, passwords, and other valuable information. Researchers are already showing how easy this attack works on Linux machines, but Microsoft says it has “not received any information to indicate that these vulnerabilities have been used to attack customers at this time.”

Protecting a Windows PC is complicated

Protecting a Windows PC is complicated right now, and there’s still a lot of unknowns. Microsoft, Google, and Mozilla are all issuing patches for their browsers as a first line of defense. Firefox 57 (the latest) includes a fix, as do the latest versions of Internet Explorer and Edge for Windows 10. Google says it will roll out a fix with Chrome 64, which is due to be released on January 23rd. Apple has not commented on how it plans to fix its Safari browser or even macOS. Chrome, Edge, and Firefox users on Windows won’t really need to do much apart from accept the automatic updates to ensure they’re protected at the basic browser level.

For Windows itself, this is where things get messy. Microsoft has issued an emergency security patch through Windows Update, but if you’re running third-party antivirus software then it’s possible you won’t see that patch yet. Security researchers are attempting to compile a list of antivirus software that’s supported, but it’s a bit of mess to say the least.

A firmware update from Intel is also required for additional hardware protection, and those will be distributed separately by OEMs. It’s up to OEMs to release the relevant Intel firmware updates, and support information for those can be found at each OEM support website. If you built your own PC you’ll need to check with your OEM part suppliers for potential fixes.

If you own a Windows-powered PC or laptop, the best thing to do right now is ensure you have the latest Windows 10 updates and BIOS updates from Dell, HP, Lenovo, or one of the many other PC makers. We’re hoping Microsoft or Intel creates a simple tool (they have a PowerShell script right now) to check protection for both the firmware and Windows updates, but until such a tool is available you’ll need to manually check or get familiar with PowerShell. Here’s a quick step-by-step checklist to follow for now:

Update to the latest version of Chrome (on January 23rd) or Firefox 57 if you use either browser

Check Windows Update and ensure KB4056892 is installed for Windows 10

Check your PC OEM website for support information and firmware updates and apply any immediately

These steps only currently provide protection against Meltdown, the more immediate threat of the CPU flaws. Spectre is still largely an unknown, and security researchers are advising that it’s more difficult to exploit than Meltdown. The New York Times reports that Spectre fixes will be a lot more complicated as they require a redesign of the processor and hardware changes, so we could be living with the threat of a Spectre attack for years to come.

Update, 1/4 9:15AM ET: Removed links to Intel’s detection tool that a now deleted Microsoft security blog may have incorrectly referenced.

Update, 1/5 10:08AM ET: Updated to clarify that ARM chips are also vulnerable to the Meltdown attack.