Which of the following is NOT a method of backing up data?

Data compression is a technique used to reduce the file size of data, making it easier to store and transmit. While it can play a significant role in optimizing storage space, it is not a method of backing up data by itself. Instead, data compression can be used in conjunction with backup methods to save space when storing backups. For instance, once data is compressed, it can then be backed up to cloud storage, a local hard drive, or an external drive.

In contrast, cloud storage, local hard drive backup, and external drive backup are all established methods for creating copies of data to protect against loss. They ensure that data can be recovered in case of hardware failure, accidental deletion, or other data loss incidents.