스팸메일이 발송되면 발ㅅㅗㄷ된 ip 뿐만 아니라 심지어는 속해있는 ip 대역까지 전체가 차단되어 선의의 피해가 유발될 수 있으며, 일단 spamhaus.org 와 같은 Black list 에 등록되면 해제하기가 쉽지 않다.
이에 대피하기 위해 정기적으로 메일 서버에 릴레이가 허용되어 있지는 않은지 점검하여야 한다. 아래 스크립트로 체크해 보면 릴레이 여부를 한꺼번에 체크할수 있다.
#!/usr/bin/perl
use Socket;
use Net::SMTP;
my $MAXPIDS=250;
my $TESTFROM="YOUR\@EMAIL.HERE";
my $TESTTO="OTHER\@EMAIL.ADDRESS";
my $HELP=q
{Usage: perl relaycheck.pl [-h | --help] host
};
my @hosts;
for $_ (@ARGV){
if(/^--(.*)/){
$_=$1;
if(/help/){
print $HELP;
exit(0);
}
}
elsif(/^-(.*)/){
$_=$1;
if(/^h/ or /^?/){
print $HELP;
exit(0);
}
}else{
push @hosts,$_;
}
}
if(!$hosts[0]){
print $HELP;
exit(-1);
}
my $host;
print "relaycheck v0.3 by dave weekly <dew\@cs.stanford.edu>\n\n";
# bury dead children
$SIG{CHLD}= sub{wait()};
# go through all of the hosts, replacing subnets with all contained IPs.
for $host (@hosts){
$_=shift(@hosts);
# scan a class C
if(/^([^.]+)\.([^.]+)\.([^.]+)$/){
my $i;
print "Expanding class C $_\n";
for($i=1;$i<255;$i++){
my $thost="$_.$i";
push @hosts,$thost;
}
}
else{
push @hosts,$_;
}
}
my @pids;
my $npids=0;
for $host (@hosts){
my $pid;
$pid=fork();
if($pid>0){
$npids++;
if($npids>$MAXPIDS){
for(1..($MAXPIDS/2)){
if(wait()>0){
$npids--;
}
}
}
next;
}elsif($pid==-1){
print "fork error\n";
exit(0);
}else{
$ARGV0="(checking $host)";
my($proto,$port,$sin,$ip);
$proto=getprotobyname('tcp');
$port=25;
$ip=inet_aton($host);
if(!$ip){
print "couldn't find host $host\n";
exit(0);
}
$sin=sockaddr_in($port,$ip);
socket(Sock, PF_INET, SOCK_STREAM, $proto);
if(!connect(Sock,$sin)){
# print "couldn't connect to SMTP port on $host\n";
exit(0);
}
close(Sock);
# SOMETHING is listening on the mail port...
my $smtp = Net::SMTP->new($host, Timeout => 30);
if(!$smtp){
# print "$host doesn't have an SMTP port open.\n";
exit(0);
}
my $domain = $smtp->domain();
# print "host $host identifies as $domain.\n";
$smtp->mail($TESTFROM);
if($smtp->to($TESTTO)){
print "SMTP host $host [$domain] relays.\n";
}else{
print "SMTP host $host [$domain] does not relay.\n";
}
$smtp->reset();
$smtp->quit();
exit(0);
}
}
print "done spawning, $npids children remain\n";
# wait for my children
$|=1;
for(1..$npids){
my $wt=wait();
if($wt==-1){
print "hey $!\n";
redo;
}else{
# print "$wt\n";
}
}
print "Done\n"; |
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