use threads;
use Socket;
use strict;
use warnings;

my $banned_type = {
    "cab" => 1,
    "class" => 1,
    "dat" => 1,
    "exe" => 1,
    "gif" => 1,
    "ico" => 1,
    "js" => 1,
    "swf" => 1
};

my $banned_site = {
    "ad.doubleclick.net" => 1,
    "lz.mainentrypoint.com" => 1,
    "search-itnow.com" => 1,
    "www.ftstock.com" => 1,
    "www.newshub.com" => 1
};

use constant RES_400 => "HTTP/1.1 400 Bad Request\r\n\r\n";

my $proto = getprotobyname('tcp');
socket(BROWSER_LISTENER, PF_INET, SOCK_STREAM, $proto) || die "Failed 
+to create socket: $!";
setsockopt(BROWSER_LISTENER, SOL_SOCKET, SO_REUSEADDR, pack("l", 1)) |
+| die "Failed to setsockopt: $!";
bind(BROWSER_LISTENER, sockaddr_in(8080, INADDR_ANY)) || die "Failed t
+o bind: $!";
listen(BROWSER_LISTENER, SOMAXCONN) || die "Failed to listen: $!";  
print "Internet filter started\n";
while (1) {
    my $browser;
    accept($browser, BROWSER_LISTENER);
    my $req;
    my $chunk;
    do {
    } until (!sysread($browser, $chunk, 10000) || ($req .= $chunk) =~ 
+m/\r\n\r\n/);
    my $host = ($req =~ m/Host:\s*(.*?)\r/)[0];
    my ($method, $page) = ($req =~ m/^(.*?)\s+(.*?)\s/);
    print "Received request for [$method, $page]\n";
    if ($host && $page) {
        if (is_banned_site($host) || is_banned_type($page)) {
            #print "[$host, $page] is banned\n";
            print $browser RES_400;
            close($browser);
        } else {
            threads->create(\&process_one_req, $browser, $req, $method
+, $host)->detach();
        }
    } else {
        close($browser);
    }
}

sub process_one_req {
    my ($browser, $req, $method, $host) = @_;
    my $iaddr = inet_aton($host) || die "no host: $host";
    my $paddr = sockaddr_in(80, $iaddr);    
    $proto = getprotobyname('tcp');
    my $remote;
    socket($remote, PF_INET, SOCK_STREAM, $proto) || die "socket: $!";
    connect($remote, $paddr) || die "connect: $!";
    print $remote $req, "\r\n";
    my $chunk;
    while (sysread($remote, $chunk, 10000)) {
        print $browser $chunk; 
    }
    close($remote);
    undef($remote);
    close($browser);
    undef($browser);
    undef($req);
    undef($host);
}

sub is_banned_site {
    my $site = shift;
    return 1 if (exists($banned_site->{$site}));

    if ($site =~ m/offeroptimizer/) {
        return 1;
    }
    if ($site =~ m/revenue.net$/) {
        return 1;
    }
    if ($site =~ m/popupsponsor.com$/) {
        return 1;
    }
    if ($site =~ m/hitbox.com$/) {
        return 1;
    }
    return 0;
}

sub is_banned_type {
    return (exists($banned_type->{(split(/\./, shift))[-1]})) ? 1 : 0;
}
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