What does your cloud storage being full have to do with a security app? If you are utilizing the Samsung Cloud or Google Cloud or actually any cloud service, your texts would say which cloud storage is full. If you are getting generic pop-ups or texts saying your cloud storage is full, clean it now, I'm afraid those are spam/phishing messages trying to get you to pay an exorbitant price for something and/or get your credit card information. If your Google cloud was full, you would get a message with the Google header, same with Samsung or Microsoft. Anything generic is not legitimate.
If they are coming as pop-ups or notifications it could be coming from a rogue app you installed. If it's coming as text messages, it's just spam.
