Google today announced it is expanding its Safe Browsing service to protect users against malware that makes unexpected changes to your computer. These threats typically take the form of helpful downloads, but they actually quietly switch your homepage, other browser settings, and in general modify operating system defaults.

Google says it will show a warning in Chrome whenever an attempt is made to trick you into downloading and installing such software. The prompts will start appearing “next week” and look just like the warnings for other forms of malware:

p Google expands its Safe Browsing service to flag malware that makes unexpected changes to your computer

You can still access the download by going to your Downloads list and manually opening the file. As you can see in the screenshot above, Google is using an example file called “pua.exe.”

In the case of malware, PUA stands for Potentially Unwanted Application, which is also sometimes called Potentially Unwanted Program or PUP. In short, the broad terms encompass any downloads that the user does not want, typically because they display popups, show ads, install toolbars in the default browser, change the homepage or the search engine, run several processes in the background that slow down the PC, and so on.

Google says that Safe Browsing currently shows more than 3 million download warnings per week, and that number is likely to increase very quickly now that the scope has broadened to more threats. In total, it is used by 1.1 billion users on the Web.

These numbers are so high because the service doesn’t just warn Chrome users about malicious websites and malicious downloads; it’s also used by Mozilla Firefox and Apple’s Safari. We’re not sure how quickly users of those browsers can expect to be warned about PUAs and PUPs, but we’ve contacted the companies involved and will update this article if and when we hear back.

Update at 7:05PM EST: Mozilla is interested in the new functionality. Apple has not responded to request for comment.

“We are happy to see that Google is continuing to improve its detection of potentially unwanted software, especially since Firefox relies on Google Safe Browsing to block malicious downloads,” a Mozilla spokesperson told TNW. “We are investigating implementing this new extension, especially if it reduces unofficial rebundled software that targets Firefox.”

See alsoGoogle unveils Project Zero: Security researchers hired solely to protect the Internet from targeted attacks and Google’s CIO explains the challenge of keeping data secure: ‘We spend a lot of time worrying about it’

Top Image Credit: KIMIHIRO HOSHINO/AFP/Getty ImagesJOHANNES EISELE/AFP/Getty Images