A systems administrator has been notified of possible illegal activities taking place on the network...

The correct answer is C. Legal hold.

A legal hold is a process that organizations use to preserve relevant electronic information when they anticipate litigation or have an active e-discovery request. A legal hold requires that certain email messages be retained and unaltered until they are no longer required for court use. Legal hold requirements apply both to the content of messages as well as the metadata which can provide proof of delivery and other critical non-repudiation information12.

Email archiving is a process that organizations use to store email messages for long-term retention, compliance, and backup purposes. Email archiving does not necessarily imply that the email messages are preserved for legal purposes, although some email archiving solutions may offer legal hold capabilities1.

Version control is a process that software developers use to manage changes to source code and other files in a project. Version control allows developers to track, compare, and revert changes, as well as collaborate with other developers. Version control does not apply to email messages or legal hold.

File integrity monitoring is a process that security professionals use to detect unauthorized or malicious changes to files and directories on a system. File integrity monitoring helps to protect the system from malware, data breaches, and configuration errors. File integrity monitoring does not apply to email messages or legal hold.