Final answer:
A technician should first run a comprehensive antivirus scan to address files set to system and hidden due to a virus.
If needed, a system restore, manual attribute change, or hard drive format might follow, with the latter used as a final measure.
Therefore, the correct answer is: option C) Manually changing file attributes
Step-by-step explanation:
When a technician is remediating a virus on an infected workstation and all user files are set to system and hidden, they should first consider running a comprehensive antivirus scan. This scan can help to identify and remove the virus, as well as restore the file attributes to their original state.
In some cases, if a virus is particularly pervasive or damaging, additional steps like conducting a full system restore or manually changing file attributes might be necessary. As a last resort, if the system is too compromised to recover, formatting the entire hard drive may be required.
However, this should only be done after backing up all recoverable and clean data, as this process will erase all information on the drive.