Dotaz: SPAM z podvržené adresy v mojí doméně.

[Honza]

Zdravím,
mám maličký poštovní server (postfix, saslauth, cyrus-imap, spamassassin) na vlastní doméně. Poslední dobou začaly na můj server chodit Delivery Status Notifications. Problém je v tom, že můj server není odesílatel, adresa je podvržená, na mém serveru neexistující. Maily na neexistující adresu chodí do schránky mě, proto o tom vůbec vím. Autorizaci k odeslání mailu musí uživatel provést přes sasl, takže nemyslím, že spamuje přímo někdo z majitele účtu u mě. Je to obyčejný spam, který nemusím řešit nebo je na místě obava z toho, že mě některé antispamy začnou na základě podvržené adresy filtrovat? Dá se nějak řešit zneužití vymyšlené adresy na existující doméně (SPF již řeším, ale stejně jsem koukal, že to zatím není moc rozšířený spůsob)? Pro jistotu přikládám konfiguraci postfixe, vzorek spamu a výpis logu.
Díky za jakoukoli pomoc. :)

main.cf

log # postconf -n
append_dot_mydomain = no
biff = no
broken_sasl_auth_clients = yes
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/lib64/postfix
disable_vrfy_command = yes
home_mailbox = .maildir/
html_directory = /usr/share/doc/postfix-2.4.6-r2/html
inet_interfaces = all
invalid_hostname_reject_code = 554
local_recipient_maps = ldap:/etc/postfix/ldap/virtual_aliases.cf
mail_owner = postfix
mailbox_transport = lmtp:unix:/var/imap/socket/lmtp
mailq_path = /usr/bin/mailq
manpage_directory = /usr/share/man
message_size_limit = 20480000
multi_recipient_bounce_reject_code = 554
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mydomain = moje-domena.cz
myhostname = moje-domena.cz
mynetworks = 127.0.0.0/8
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases
non_fqdn_reject_code = 554
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.4.6-r2/readme
relay_domains_reject_code = 554
sample_directory = /etc/postfix
sendmail_path = /usr/sbin/sendmail
setgid_group = postdrop
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks,            
                          reject_non_fqdn_hostname,               
                          reject_invalid_hostname,                
                          regexp:/etc/postfix/helo.regexp
smtpd_recipient_restrictions = permit_sasl_authenticated,               
                               permit_mynetworks,              
                               reject_invalid_hostname,                
                               reject_non_fqdn_hostname,        
                               reject_non_fqdn_sender,          
                               reject_non_fqdn_recipient,              
                               reject_unknown_sender_domain,           
                               reject_unknown_recipient_domain,               
                                reject_unlisted_recipient,            
                                reject_unverified_sender,           
                                reject_multi_recipient_bounce,          
                                reject_unauth_destination,              
                                reject_unverified_recipient             
                                reject_rbl_client zen.spamhaus.org,               
                                reject_rbl_client cbl.abuseat.org,      
                                reject_rhsbl_client blackhole.securitysage.com,     
                                reject_rhsbl_sender blackhole.securitysage.com,               
                                reject_rhsbl_sender dsn.rfc-ignorant.org,           
                                reject_rbl_client blackholes.easynet.nl,        
                                reject_rbl_client proxies.blackholes.wirehub.net,       
                                reject_rbl_client bl.spamcop.net,         
                                reject_rbl_client dnsbl.njabl.org,          
                                reject_rbl_client dev.null.dk,          
                                reject_rbl_client dnsbl.ahbl.org,               
                                reject_rbl_client combined.rbl.msrbl.net,         
                                reject_rbl_client multi.uribl.com,              
                                reject_unauth_destination,              
                                check_policy_service unix:private/policy
smtpd_reject_unlisted_recipient = yes
smtpd_sasl_auth_enable = yes
smtpd_sasl_authenticated_header = yes
smtpd_sasl_path = smtpd
smtpd_sasl_security_options = noanonymous
smtpd_sasl_tls_security_options = noanonymous
smtpd_tls_cert_file = /usr/src/install/klice/server.crt
smtpd_tls_key_file = /usr/src/install/klice/server.key
smtpd_tls_loglevel = 2
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
smtpd_use_tls = yes
strict_rfc821_envelopes = yes
tls_random_source = dev:/dev/urandom
unknown_address_reject_code = 554
unknown_client_reject_code = 554
unknown_hostname_reject_code = 554
unknown_local_recipient_reject_code = 554
unknown_relay_recipient_reject_code = 554
unknown_virtual_alias_reject_code = 554
unknown_virtual_mailbox_reject_code = 554
unverified_recipient_reject_code = 554
unverified_sender_reject_code = 554
virtual_alias_maps = ldap:/etc/postfix/ldap/virtual_aliases.cf

vzorek spamu:

From - Thu Jun 11 08:40:26 2009
X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Return-Path: <>
Received: from moje-domena.cz ([unix socket])
	 by muj-server (Cyrus v2.3.9-Gentoo) with LMTPA;
	 Thu, 11 Jun 2009 08:15:08 +0200
X-Sieve: CMU Sieve 2.3
Received: by moje-domena.cz (Postfix, from userid 1005)
	id 5695D3C57E; Thu, 11 Jun 2009 08:15:08 +0200 (CEST)
X-Spam-Checker-Version: SpamAssassin 3.2.1-gr1 (2007-05-02) on
	muj-server.moje-domena.cz
X-Spam-Level: 
X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=ham
	version=3.2.1-gr1
Received-SPF: none (mail.gocontact.pt: No applicable sender policy available) receiver=muj-server.moje-domena.cz; identity=helo; helo=mail.gocontact.pt; client-ip=213.63.137.179
Received: from mail.gocontact.pt (mail.gocontact.pt [213.63.137.179])
	by moje-domena.cz (Postfix) with ESMTP id 9D88B3A61C
	for <upland@moje-domena.cz>; Thu, 11 Jun 2009 08:15:01 +0200 (CEST)
Received: from localhost (localhost.localdomain [127.0.0.1])
	by mail.gocontact.pt (Postfix) with ESMTP id 4DAD3AC5EE
	for <upland@moje-domena.cz>; Thu, 11 Jun 2009 07:15:05 +0100 (WEST)
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
Received: from mail.gocontact.pt ([127.0.0.1])
	by localhost (mail.gocontact.pt [127.0.0.1]) (amavisd-new, port 10024)
	with ESMTP id SRaBcJYreltb for <upland@moje-domena.cz>;
	Thu, 11 Jun 2009 07:15:02 +0100 (WEST)
Received: from scalix.procompe.pt (scalix [192.168.8.23])
	by mail.gocontact.pt (Postfix) with ESMTPS id 8DCADAC5F3
	for <upland@moje-domena.cz>; Thu, 11 Jun 2009 07:14:51 +0100 (WEST)
Received: from localhost (localhost)
	by scalix.procompe.pt (8.13.8/8.13.8) id n5B6FR8m031465;
	Thu, 11 Jun 2009 07:16:09 +0100
Date: Thu, 11 Jun 2009 07:16:09 +0100
From: Mail Delivery Subsystem <MAILER-DAEMON@scalix.procompe.pt>
Message-Id: <200906110616.n5B6FR8m031465@scalix.procompe.pt>
To: <upland@moje-domena.cz>
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
	boundary="n5B6FR8m031465.1244700969/scalix.procompe.pt"
Subject: Returned mail: see transcript for details
Auto-Submitted: auto-generated (failure)

This is a MIME-encapsulated message

--n5B6FR8m031465.1244700969/scalix.procompe.pt

The original message was received at Thu, 11 Jun 2009 06:42:27 +0100
from localhost.localdomain [127.0.0.1]

   ----- The following addresses had permanent fatal errors -----
<bastos@procompe.pt>
    (reason: 554 5.4.6 Too many hops)

   ----- Transcript of session follows -----
554 5.4.6 Too many hops 30 (25 max): from <upland@moje-domena.cz> via localhost, to <bastos@procompe.pt>

--n5B6FR8m031465.1244700969/scalix.procompe.pt
Content-Type: message/delivery-status

Original-Envelope-Id: 289027011335207204@moje-domena.cz
Reporting-MTA: dns; scalix.procompe.pt
Arrival-Date: Thu, 11 Jun 2009 06:42:27 +0100

Final-Recipient: RFC822; bastos@procompe.pt
Action: failed
Status: 5.4.6
Diagnostic-Code: SMTP; 554 5.4.6 Too many hops
Last-Attempt-Date: Thu, 11 Jun 2009 07:16:09 +0100

--n5B6FR8m031465.1244700969/scalix.procompe.pt
Content-Type: message/rfc822

Return-Path: <upland@moje-domena.cz>
Received: from scalix.procompe.pt (localhost.localdomain [127.0.0.1])
	by scalix.procompe.pt (8.13.8/8.13.8) with ESMTP id n5B5gD8f028557
	for <bastos@procompe.pt>; Thu, 11 Jun 2009 06:42:27 +0100
...
Received: from spxsez.telecomitalia.it (host130-232-dynamic.20-87-r.retail.telecomitalia.it [87.20.232.130])
	by mail.gocontact.pt (Postfix) with SMTP id 6E48BAC5E0
	for <bastos@procompe.pt>; Wed, 10 Jun 2009 19:57:18 +0100 (WEST)
Date: Wed, 10 Jun 2009 18:57:18 +0000
From: Tanigawa <upland@moje-domena.cz>
To: bastos@procompe.pt
Message-ID: <289027011335207204@moje-domena.cz>
Subject: Hungary plaans to turn jails into luxury hotels
x-scalix-Hops: 1
x-scalix-Transport-Id: <289027011335207204@moje-domena.cz>
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
X-Virus-Scanned: Debian amavisd-new at mail.gocontact.pt
X-Mailer: PHP v5.1.6
MIME-Version: 1.0
Content-Type: multipart/mixed;
	boundary="-------FQV3dczmHoRWXA6IVcvuZKBOLiL30y0"

---------FQV3dczmHoRWXA6IVcvuZKBOLiL30y0
Content-Type: text/plain;
	charset="US-ASCII"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

Hi, my pohto attached
---------FQV3dczmHoRWXA6IVcvuZKBOLiL30y0
Content-Type: image/png;
	name="henchman.png"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
	filename="henchman.png"

a odpovídající záznam v logu

Jun 11 08:15:01 muj-server postfix/smtpd[7887]: connect from mail.gocontact.pt[213.63.137.179]
Jun 11 08:15:04 muj-server postfix/policy-spf[7892]: handler sender_policy_framework: is decisive.
Jun 11 08:15:04 muj-server postfix/policy-spf[7892]: : Policy action=PREPEND Received-SPF: none (mail.gocontact.pt: No applicable sender policy available) receiver=muj-server.moje-domena.cz; identity=helo; helo=mail.gocontact.pt; client-ip=213.63.137.179
Jun 11 08:15:04 muj-server postfix/smtpd[7887]: 9D88B3A61C: client=mail.gocontact.pt[213.63.137.179]
Jun 11 08:15:04 muj-server postfix/cleanup[7894]: 9D88B3A61C: message-id=<200906110616.n5B6FR8m031465@scalix.procompe.pt>
Jun 11 08:15:04 muj-server postfix/qmgr[17914]: 9D88B3A61C: from=<>, size=26052, nrcpt=2 (queue active)
Jun 11 08:15:04 muj-server postfix/smtpd[7887]: disconnect from mail.gocontact.pt[213.63.137.179]
Jun 11 08:15:08 muj-server postfix/qmgr[17914]: 9D88B3A61C: removed
Jun 11 08:15:08 muj-server postfix/pickup[6868]: 5695D3C57E: uid=1005 from=<MAILER-DAEMON>
Jun 11 08:15:08 muj-server postfix/cleanup[7894]: 5695D3C57E: message-id=<200906110616.n5B6FR8m031465@scalix.procompe.pt>
Jun 11 08:15:08 muj-server postfix/pipe[7895]: 9D88B3A61C: to=<@moje-domena.cz>, orig_to=<upland@moje-domena.cz>, relay=spamfilter, delay=6.7, delays=3.3/0.01/0/3.4, dsn=2.0.0, status=sent (delivered via spamfilter service)
Jun 11 08:15:08 muj-server postfix/pipe[7895]: 9D88B3A61C: to=<upland@moje-domena.cz>, relay=spamfilter, delay=6.7, delays=3.3/0.01/0/3.4, dsn=2.0.0, status=sent (delivered via spamfilter service)
Jun 11 08:15:08 muj-server postfix/qmgr[17914]: 5695D3C57E: from=<>, size=26355, nrcpt=3 (queue active)
Jun 11 08:15:08 muj-server postfix/lmtp[7903]: 5695D3C57E: to=<moje-schranka@moje-domena.cz>, orig_to=<@moje-domena.cz>, relay=moje-domena.cz[/var/imap/socket/lmtp], delay=3.4, delays=3.3/0.01/ 0.02/0.02, dsn=2.1.5, status=sent (250 2.1.5 Ok)
Jun 11 08:15:08 muj-server postfix/lmtp[7903]: 5695D3C57E: to=<upland@moje-domena.cz>, relay=moje-domena.cz[/var/imap/socket/lmtp], delay=3.4, delays=3.3/0.05/0/0.01, dsn=5.1.1, status=bounced (host moje-domena.cz[/var/imap/socket/lmtp] said: 550-Mailbox unknown.  Either there is no mailbox associated with this 550-name or you do not have authorization to see it. 550 5.1.1 User unknown (in reply to RCPT TO command))
Jun 11 08:15:08 muj-server postfix/lmtp[7903]: 5695D3C57E: to=<moje-schranka@moje-domena.cz>, orig_to=<upland@moje-domena.cz>, relay=moje-domena.cz[/var/imap/socket/lmtp], delay=3.4, delays=3.3/0.06/0.01/0, dsn=2.1.5, status=sent (250 2.1.5 Ok)
Jun 11 08:15:08 muj-server postfix/qmgr[17914]: 5695D3C57E: removed

Odpovědi

[Masca]

Není moc jak se tomu bránit, holt po světě běhají maily s vymyšlenými adresami. Něco se dá trochu vylepšit podle www.postfix.org/BACKSCATTER_README.html.

[Pepe II]

Non delivery reporty (NDR) se daji eliminovat pridanim "fingerprintu" do hlavicky mailu pri odesilani. Pokud pak prichozi NDR neobsahuje muj fingerprint, tak se zahazuje. Reseni je v napr. v MailScanneru (http://www.mailscanner.info).