When the packages ntfs-3g and gnome-mount are installed from the official repositories, ntfs partitions, listed under "computer:///" in nautilus, may be mounted by double-clicking them. However, all directories and files have permissions set to 777. I want files to have permissions set to 666 (no execute).
For most partition types, gnome-mount will honor options set at /system/storage/default_options/ in gconf. I added noatime and noexec to most non-ntfs partition types, such as vfat, but noexec has no effect when used with ntfs-3g.
The ntfs-3g man page indicates that the mount option fmask=0111 will change the file permissions to 666 while leaving the directory permissions alone. The fmask option is not recognized by gnome-mount, and adding it in the gconf will result in error messages from gnome-mount. The related option umask is supported by gnome-mount, but will make navigating directories impossible.
gnome-mount uses the symbolic link, /sbin/mount.ntfs-3g, to mount partitions ntfs-3g partitions. Replacing the symbolic link with a script that uses appropriate mount options should give the desired effects.
sudo unlink /sbin/mount.ntfs-3g
sudo nano /sbin/mount.ntfs-3g
in nano, type:
#!/bin/bash
/usr/bin/ntfs-3g -o fmask=0111,noatime "$@"
Files in ntfs partitions mounted through nautilus should now have permissions set to 666. Don't forget to unmount partitions before removing external drives.