I was looking through a backup of my DOS hdd connected to my Windows machine, and noticed IO.IDX, which wasn't on my new hdd that I'd just installed DOS 6.22 on. I did some googling and couldn't find anything definitive on what this file was. All I know for sure is it's 101 bytes and the date stamp on it is March 30th of this year. Here is the virustotal.com analysis:
https://virustotal.com/en/file/bb8450c888729e … sis/1469101797/

Could it have been created by NU? I did mess with NU briefly awhile back.