I'm trying to mount a Windows 10 share on xubuntu 16.04 using /etc/fstab and I noticed that if I don't set "file_mode=0777,dir_mode=0777" as parameters in "/etc/fstab", users outside of root are unable to write to the share. This seemed like a security risk to me at first since I saw that 777 means that everyone should have permissions to read and write to the share which I didn't want. So I instead deleted those parameters, looks at the manual and instead set gid=1000 so only the users in that group would be able to write to the share. This didn't end up working at all so I put back the "file_mode=0777" and "dir_mode=0777" parameters into /etc/fstab and it worked just how I wanted it to work. According to thunar, users in group 1000 are able to r&w whilst "Others" don't have any access.
tl;dr: Why do you need the file_mode=0777 and dir_mode=0777 parameters in order to get proper permissions on a share? And if 0777 in octal permissions means everyone has access to it, then why does the parameter "gid=1000" seem to override it?