What is the most likely cause of a user experiencing pop-ups and spam after receiving digital promotional materials?

The situation described indicates that the user is experiencing pop-ups and spam after receiving digital promotional materials, which suggests that their system may have been infected with malicious software. The most likely cause is that malicious code was transferred via the USB drive, especially if the promotional materials were stored on it.

When a USB drive contains harmful software, connecting it to a system can initiate the execution of that code, leading to various issues including unwanted pop-ups, spam, or other intrusive behaviors. Such infections often manifest in the form of adware, which is designed to display unsolicited advertisements and can clutter the user’s browsing experience.

In contrast, drive-by downloads typically occur when a user visits a malicious or compromised website rather than receiving materials through a USB. An installed cryptominer usually operates silently in the background and doesn’t directly generate pop-ups or spam but focuses on using system resources to mine cryptocurrency. A corrupted operating system might lead to performance issues or application failures but is less likely to cause immediate pop-ups and spam unless related malware is also present. Therefore, the scenario aligns more closely with the transmission of malicious code through the USB drive.