Which of the following types of malware is this example of?

A security consultant is analyzing data from a recent compromise.

The following data points are documented

• Access to data on share drives and certain networked hosts was lost after an employee logged in to an interactive session as a privileged user.

• The data was unreadable by any known commercial software.

• The issue spread through the enterprise via SMB only when certain users accessed data.

• Removal instructions were not available from any major antivirus vendor.

Which of the following types of malware is this example of?
A . RAT
B . Ransomware
C . Backdoor
D . Keylogger
E . Worm