What malware distribution technique exploits flaws in browser software to install malware upon visiting a web page?

The correct answer is the technique known as drive-by downloads. This method takes advantage of vulnerabilities present in web browsers or their plugins. When a user visits a compromised or harmful website, the exploit code embedded in the page can be leveraged to automatically download and install malware onto the user's system without their knowledge or consent. This makes drive-by downloads particularly dangerous, as they can occur without any user interaction aside from simply visiting a webpage.

In comparison to the other choices, email attachments require the user to open or execute the attachment for malware to be installed. File sharing typically involves users willingly sharing files between different systems, which usually does not exploit browser vulnerabilities. Malicious advertisements, while they can lead to drive-by downloads, are a broader category and do not directly describe the specific exploitation of browser flaws that is characteristic of drive-by downloads. Therefore, drive-by downloads are the most accurate descriptor of the technique that exploits browser vulnerabilities to install malware.