If you suspect your SecureKey has been compromised, you are advised to switch to a secondary SecureKey as your Signing SecureKey:
Navigate to the sidebar menu > Settings > SecureKey.
Navigate to Signing SecureKey and select Change SecureKey.
Select one of your secondary SecureKeys from the dropdown list.
Sign with your SecureKey to approve the request.
Your new SecureKey address will be reflected on the Signing SecureKey section.
Watch this video tutorial for a step-by-step walkthrough:
Note: By changing your Signing SecureKey, your original SecureKey will no longer be available for trading on GRVT, unless its a GRVT SecureKey secured by Dfns.
Also, as shown in the below diagram, replacing your current Signing SecureKey with a Secondary SecureKey won't change your Funding Account address, which stays as the address of your first registered SecureKey.