Why would InDesign add text (in another language, if it is one) without my inserting new text?

I discovered today that the end of my long file has text that appears to be in Spanish or Italian. But I doubt it's a real language. I did not add text to the end. Did this happen because of a virus or hack? If anyone else has had this happen, please tell me. And if you know how to prevent it, please tell me. Thank you.