We have that file popping out on some of our websites(x5fet5.txt) and getting quarantined. Is that file generated by webhost or by plugins (BPS Pro?) ?
When BPS automatically creates a file a backup copy of the file is also copied to /bps-backup at the same time the file is created. This is not a BPS file. Open the file in Quarantine using the View File option to see the contents of that file. Since this is a text file then it is probably not malicious and is some sort of log file. Post the contents of the file and I will take a guess at what it goes with or is doing.