[declan@localhost default]$ whoami
declan
[declan@localhost default]$ tail -n 1 /etc/group
firefox:x:1000:declan
[declan@localhost default]$ ls -l /usr/lib/firefox/firefox
-rwxr-xr--  1 root firefox 5258 Dec  5  2005 /usr/lib/firefox/firefox
[declan@localhost default]$ /usr/lib/firefox/firefox
bash: /usr/lib/firefox/firefox: Permission denied
[declan@localhost default]$