@ Permissions for files in Mac system

If the file or directory has an extended attribute, the LS command, when executed with the-l option, is appended with a character @ after the permission field.
If the file or directory has extended security information, when the LS command is executed with the-l option, a character + is appended to the Permissions permission field.

If the file or directory has extended
Attributes, the Permissions field printed by The-l option was followed by
A ' @ ' character. Otherwise, if the file or directory has extended secu-
rity information, the Permissions field printed by The-l option is fol-
Lowed by a ' + ' character.

See Man LS (1) on Max OS X

@ Permissions for files in Mac system