I recently came across this message when I was downloading a word document via google drive. This document came from a trusted source as well. Security alert! We found that there might be viruses, spyware, or other potentially unwanted programs in the file you are trying to download. Then it asks to block download or accept the risk. Knowing the source and what was in the document in the preview, I went and downloaded it anyways without any issues. I'm just trying to figure out why I am getting these messages all of a sudden. These documents do contain links to picture files on the web, I was wondering if maybe embedded urls trip the security system. Anyways, it was kind of annoying and was trying to get to the source. Let me know if you need more info.