Answer:
The changes to BEST counter the threat presented in this scenario is  Implement NAC to check for updated anti-malware signatures and location-based rules for PCs connecting to the internal network.
Explanation:
Implementing Network access Control NAC to check for updated anti-malware signatures and location-based rules for PCs connecting to the internal network.Network Access Control (NAC) is the best reedy that will not alter the existing work schedule in place.
This approach to computer security will unify endpoint security technology such as antivirus, host intrusion prevention, and vulnerability assessment for all users and foster stronger system authentication.
NAC will reinforce and strengthen the network security in order to prevent internal server issues from any contractor or employee henceforth.