"To obtain a forensically sound image from nonvolatile storage, you need to ensure that nothing you do alters data or metadata (properties) on the source disk or file system. A write blocker assures this process by preventing any data on the disk or volume from being changed by filtering write commands at the driver and OS level. Data acquisition would normally proceed by attaching the target device to a forensics workstation or field capture device equipped with a write blocker."
For purposes of knowing, https://security.opentext.com/tableau/hardware/details/t8u write blockers like this are the most popular hardware blockers

https://ktechproducts.com/Data-mask#:~:text=Data%20Masking%20is%20a%20method%20of%20creating%20a,partial%20data%20based%20on%20the%20user%E2%80%99s%20security%20permissions.
The main reason for applying masking to a data field is to protect data that is classified as personally identifiable information, sensitive personal data, or commercially sensitive data. However, the data must remain usable for the purposes of undertaking valid test cycles. It must also look real and appear consistent. It is more common to have masking applied to data that is represented outside of a corporate production system. In other words, where data is needed for the purpose of application development, building program extensions and conducting various test cycles https://en.wikipedia.org/wiki/Data_masking