CAS-001 Question #102: Real Exam Question with Answer & Explanation

The root cause analysis of a recent security incident reveals that an attacker accessed a printer from the Internet. The attacker then accessed the print server, using the printer as a launch pad for a shell exploit. The print server logs show that the attacker was able to exploit multiple accounts, ultimately launching a successful DoS attack on the domain controller. Defending against which of the following attacks should form the basis of the incident mitigation plan?