map $http_user_agent $bad_user_agent {

    default                           0;

    "~*backdoor"                      1;
    "~LieBaoFast"                     1;
    "~AhrefsBot"                      1;
    "~DotBot"                         1;
    "~MauiBot"                        1;
    "~MJ12Bot"                        1;
    "~PetalBot"                       1;
    "~PetalBot"                       1;
    "~SEMrushBot"                     1;
    "~UCBrowser"                      1;
}