Google has updated its Safe Browsing feature to block a greater range of malware making surprise changes to victims' computers.
The feature is relied on to protect users of several widely used web browsers, including Google Chrome, Mozilla Firefox and Apple Safari.
Moheeb Abu Rajab, staff engineer at Google Security, said: "Our Safe Browsing service protects you from malicious websites and warns you about malicious downloads in Chrome.
"We're currently showing more than three million download warnings per week -- and because we make this technology available for other browsers to use, we can help keep 1.1 billion people safe."
According to data from Google's transparency report, Safe Browsing across Chrome, Firefox and Safari issued 13-26 million users warnings every week since the start of the year.
"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," Mozilla said.
"We are investigating implementing this new extension, especially if it reduces unofficial rebundled software that targets Firefox."