Nginx - User Agent Blocking

Nginx - User Agent Blocking adalah 

set $block_user_agents 0;

if ($http_user_agent ~ "Indy Library") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "libwww-perl") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "GetRight") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "GetWeb!") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "Go!Zilla") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "Download Demon") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "Go-Ahead-Got-It") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "TurnitinBot") {
    set $block_user_agents 1;
}
if ($http_user_agent ~ "GrabNet") {
    set $block_user_agents 1;
}
if ($block_user_agents = 1) {
    return 403;
}