So I've noticed something strange with my phone. On occasion I will get a file download via text on my phone from frequent contacts. It shows up like they sent a failed picture transfer and gives me a download button. When I download the file, it vanishes. When asking the contact about it they say they sent nothing, and frequently get these from me as well. Is this normal? Seems like malware spreading to me.. Should I be concerned? Not sure that this is the right place to ask but I figured it couldn't hurt.