Today is World Backup Day!
I want to remind everybody reading this to double-check that your Sophos Firewall is saving a backup and you know the password!
Performing a backup with Sophos Firewall is simple and straightforward:
1. In-Product Backup: You can use the built-in backup options (Local, FTP, and Email).
2. Sophos Central Backup: You can also save a backup to Sophos Central (enabled by default).
https://docs.sophos.com/central/customer/help/en-us/ManageYourProducts/FirewallManagement/FirewallBackup/index.html 
Both methods can be enabled at the same time—this way, you have backups stored in Central as well as via Email, ensuring you are prepared for any situation. A good feature of Central is that it gives you the option to encrypt the backup password when you download it, so you don’t have to remember the original password.
Additionally, I want to highlight the importance of the Secure Storage Master Key (SSMK).
https://docs.sophos.com/nsg/sophos-firewall/21.0/help/en-us/webhelp/onlinehelp/AdministratorHelp/BackupAndFirmware/BackupAndRestore/BackupAndRestoreSSMK/index.html
SFOS uses the SSMK to protect sensitive data; to restore a backup with all information intact, you must have the SSMK password. If you are unsure or cannot find your SSMK password in your password manager, you can easily change the SSMK on an active system.
https://docs.sophos.com/nsg/sophos-firewall/21.0/help/en-us/webhelp/onlinehelp/CommandLineHelp/SystemSettings/ResetSSMK/index.html
Keep in mind, if you change the SSMK, it will be used for all NEW backups.
The old SSMK Password would be still good for old backups.
How to test your password/SSMK password:
You can use your backup in V20.0 MR2+ and cancel at the Port Mapping process:
Restore process will prompt you: Wrong Password; Wrong SSMK, if everything is correct, you will see the Backup/Restore Assistant: 
Here you can click Cancel.
If unsure, you can also try to restore your backup to a virtual machine.
Added TAGs
[edited by: Raphael Alganes at 1:50 PM (GMT -7) on 31 Mar 2025]
Quote