A+ Pop Quiz: This time. A system administrator has discovered malware on a computer. The computer has all of the latest security patches and is up to date with the latest anti-malware signatures. Which of the following is the MOST likely reason for this malware infection? A) Brute force attack B) Denial of service C) Zero-day attack D) Spoofing E) Man-in-the-middle attack F) I didn't click anything this time