Which of the following is MOST likely the cause of the reported issue?

A user recently attended an exposition and received some digital promotional materials The user later noticed blue boxes popping up and disappearing on the computer, and reported receiving several spam emails, which the user did not open.

Which of the following is MOST likely the cause of the reported issue?
A . There was a drive-by download of malware
B . The user installed a cryptominer
C . The OS was corrupted
D . There was malicious code on the USB drive

Answer: D