Today's web browsers are much more powerful than earlier generations of browsers. They're able to manipulate data within both the browser and the computer's local file system. Users can send and receive email, listen to music or watch a movie within a browser with the click of a button.

Unfortunately, these capabilities also mean that hackers can find clever ways to abuse the browsers to trick you into letting ransomware lock up your files when you think that you're simply doing your usual tasks online.

I'm a computer scientist who studies cybersecurity. My colleagues and I have shown how hackers can gain access to your computer's files via the File System Access Application Programming Interface (API), which enables web applications in modern browsers to interact with the users' local file systems.

The threat applies to Google's Chrome and Microsoft's Edge browsers but not Apple's Safari or Mozilla's Firefox. Chrome accounts for 65% of browsers used, and Edge accounts for 5%. To the best of my knowledge, there have been no reports of hackers using this method so far.

My colleagues, who include a Google security researcher, and I have communicated with the developers responsible for the File System Access API, and they have expressed support for our work and interest in our approaches to defending against this kind of attack. We also filed a security report to Microsoft but have not heard from them.

Double-edged sword

Today's browsers are almost operating systems unto themselves. They can run software programs and encrypt files. These capabilities, combined with the browser's access to the host computer's files – including ones in the cloud, shared folders and external drives – via the File System Access API creates a new opportunity for ransomware.