map $http_user_agent $bad_user_agent {
default 0;
"~*backdoor" 1;
"~LieBaoFast" 1;
"~AhrefsBot" 1;
"~DotBot" 1;
"~MauiBot" 1;
"~MJ12Bot" 1;
"~PetalBot" 1;
"~SEMrushBot" 1;
"~UCBrowser" 1;
}