Which step is NOT part of securing computer networks against insider threats?

Allowing open file sharing is not a step in securing computer networks against insider threats because it creates an environment where unauthorized access to sensitive data is easily facilitated. Open file sharing can lead to excessive exposure of files and data to all users within the network, increasing the risk of an insider misusing the available information. By not restricting or controlling file sharing, organizations make it difficult to monitor who accesses what, thus negating efforts to mitigate insider threats.

In contrast, configuring firewalls, monitoring outbound HTTP and HTTPS traffic, and reducing transfers to authorized users all represent proactive measures aimed at protecting the network from potential misuse. Firewalls act as barriers to unauthorized access, monitoring traffic helps in detecting anomalies that may indicate malicious behavior, and limited file transfers ensure that sensitive information is only accessible to those who have a legitimate need, significantly reducing the risk posed by insider threats.