Final answer:
The security analyst should implement a router Access Control List (ACL) to mitigate the vulnerability shown in the ICMP echo request/reply packet capture. Option B is correct.
Step-by-step explanation:
The student's question regards a security analyst reviewing a packet capture showing communication between a host and a company's router via ICMP echo requests and replies. The student is concerned about the potential vulnerability exposed by this type of communication and seeks advice on mitigating it.
To address this vulnerability, the security analyst should consider implementing a router Access Control List (ACL). An ACL will effectively control what type of traffic is allowed or blocked going through the router, which can include restricting unnecessary ICMP traffic.
Updating the router code is another possible countermeasure, but without knowing the specifics of the vulnerability, it is difficult to assert if a code update would resolve it. Disconnecting the host is a drastic and mostly temporary fix, which may not be effective long-term.
Installing the latest antivirus definitions is important for overall security, but it does not directly address network-based vulnerabilities such as unwanted ICMP traffic. Lastly, deploying a network-based IPS (Intrusion Prevention System) can be an effective method to detect and prevent various network threats, but it is more complex and resource-intensive than an ACL.
Therefore, the most direct and least disruptive action would be to implement a router ACL to limit or control ICMP traffic and help close the vulnerability.