Setting default mount options for FAT filesystems

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When I attach a FAT-formatted USB drive to my Fedora system, it gets mounted automatically. This is super convenient! But Fedora mounts it such that files and directories are world-readable...which, if you're trying to store ssh keys on a FAT-formatted thumb drive, is a problem.

I would like to set the dmask and fmask mount options that Fedora uses when automatically mounting FAT devices. How do I do this?