Canceling a masking job will terminate the execution of a masking job and re-enable all the packages and triggers that were disabled as part of job execution. When canceling a masking job there are no guarantees on the state of the data. Some fields might be fully masked, others might be partially masked while others might not be masked at all.
To cancel a Masking Job, click the Terminate button in the row for the job that is running. Confirm the action in the dialogue that appears by clicking Terminate again.