What recommendation would BEST mitigate the impact of a worm infection across the network in the future?

Segmenting the network with firewalls is the best recommendation to mitigate the impact of a worm infection across the network in the future. This approach involves dividing the network into smaller, isolated segments that can operate independently. By doing so, if a worm does manage to infect one segment, its ability to spread to other segments is significantly reduced, thereby containing the threat and minimizing overall damage.

Network segmentation limits the pathways available for worms to propagate. Each segment can be monitored and controlled more effectively, allowing for better detection and response to malicious activities. Additionally, implementing strict traffic rules between segments can further hinder the movement of the worm.

In contrast, installing a network intrusion detection system (NIDS) may help identify ongoing threats but won't actually prevent a worm from spreading once it infiltrates the system. Updating antivirus signatures daily is an important practice for catching known threats but may not be effective against new or unknown worms. Implementing application blacklisting could enhance security by preventing the execution of unauthorized applications, but it does not directly address the network spread of worms that exploit vulnerabilities within allowed applications. Thus, while all options contribute to an overall security strategy, network segmentation is the most effective proactive measure against the spread of a worm infection.