To address a maintenance problem, a vendor needs remote access to a critical network. The MOST secure
and effective solution is to provide the vendor with a:

A.
Secure Shell (SSH-2) tunnel for the duration of the problem.

B.
two-factor authentication mechanism for network access.

C.
dial-in access.

D.
virtual private network (VPN) account for the duration of the vendor support contract.

Explanation:
For granting temporary access to the network, a Secure Shell (SSH-2) tunnel is the best approach. It has
auditing features and allows restriction to specific access points. Choices B, C and D all give full access to the
internal network. Two-factor authentication and virtual private network (VPN) provide access to the entire
network and are suitable for dedicated users. Dial-in access would need to be closely monitored or reinforced
with another mechanism to ensure authentication to achieve the same level of security as SSH-2.