You can use a conditional tag to check if the user is logged in. Conditionals are very common in W, I would suggest you give this page a read.
Here is an example.
function footer_shortcode(){
if (is_user_logged_in()){
echo '
// Logged In Content
';
}else{
echo '
// Logged Out Content
';
}
}
add_shortcode('footerShortcode', 'footer_shortcode');