AT+QFLST shows a "security/" file that can't be deleted

On my BG770:

(Responses in bold)
// Delete all files
AT+QFDEL=“*”
OK

// List all files
AT+QFLST
+QFLST: “security/”,0
OK

Does anyone know what that “security/” item is?
It somewhat looks like a directory, but there are no AT+ commands to create dirs, nor to remove dirs, so it’s mysterious.
I’ll say that the item’s presence doesn’t seem to have any adverse effects on what I’m doing, but I’ still curious.

Thanks!
-Dave

Hi,
This is a file that comes with the module and will not have any impact on your use. You can ignore this file.