If you run a website or mail server in France, your server logs may show connection attempts from all three ISPs. A log rotation script could have named the file based on the first few lines of content: e.g., error codes 20 and 869 involving Orange, Wanadoo, and SFR domains.
Avoid such cryptic filenames by modifying your logging script. Instead of: -20-869---orange.fr--wanadoo.fr--sfr.fr-.txt