Block spoofing emails

We are using UTM as our mail gateway, lately, a lot of our users have received spoofing emails that appear from themself.

We use emailspooftest dotcom site to test our mail servers, and it detects the problem was 

Internal authentication is not enforced.

Fix: On inbound email gateways, only allow specific IP addresses to send mail from internal domains or force an auth challenge for internal domains. This is typically a relay setting.

Could anyone suggest how to fix this problem in Sophos? 

Parents
  • Hi,

    I recommend setting SPF-records for your domain and enabling "Perfom SPF check" in SMTP->Antispam.

    bye Josef

    BERGMANN engineering & consulting GmbH, Wien/Austria

  • Hi Josef, thank you for your reply. 

    SPF is always enabled and records are update-to-date, this seems to be an open relay problem in UTM.

  • Hi dirkkotte, 

    I can confirm the SPF is configured ok, we tested it many times on different testing sites and there are no issues.

    I did the "open-relay-test" as you suggested, which seems to be an open relay, any suggestions on how to fix it in UTM, our MX records are all pointing to the UTM 9 server


  • This kooks like my installations.

    Please check the UTM-Mail-log (within mail-manager). There i have "blocked - relay not permitted"

    Do you really activate SPF filtering at UTM?


    Dirk

    Systema Gesellschaft für angewandte Datentechnik mbH  // Sophos Platinum Partner
    Sophos Solution Partner since 2003
    If a post solves your question, click the 'Verify Answer' link at this post.

  • Yes, SPF filter is enabled 

  • I cannot see "blocked - relay not permitted" in Mail Manager.

  • just send an email from an external source as postmaster@yourdomain through the firewall and you have your open relay... no checks at all will be applied...

  • Which result do you see for the mail from supertool@mxtoolboxsmtpdiag.com to test@mxtoolboxsmtpdiag.com ?


    Dirk

    Systema Gesellschaft für angewandte Datentechnik mbH  // Sophos Platinum Partner
    Sophos Solution Partner since 2003
    If a post solves your question, click the 'Verify Answer' link at this post.

  • Hi,

    maybe you are completely on the wrong track, I don't think that there is a open relay problem in the UTM.

    What was your problem:

    lot of our users have received spoofing emails that appear from themself

    How exactly look this emails? Are the spoofed senders email-addresses maybe only in the body and not in the envelope FROM. Check the SMTP Log in the Mail Manager, what exactly is the from address here.

    If these from-domain is your domain, then check your SPF-domainsettings in your DNS.

    bye Josef

    BERGMANN engineering & consulting GmbH, Wien/Austria

  • This is the email header looks like


    Received: from EX2016-MDB-C.MYDOMAIN.Hosted (10.2.4.212) by
     EX2016-MDB-C.MYDOMAIN.Hosted (10.2.4.212) with Microsoft SMTP Server
     (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8
     via Mailbox Transport; Wed, 4 May 2022 04:16:58 +1000
    Received: from EX2016-MDB-AN.MYDOMAIN.Hosted (10.2.2.129) by
     EX2016-MDB-C.MYDOMAIN.Hosted (10.2.4.212) with Microsoft SMTP Server
     (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id
     15.1.2308.8; Wed, 4 May 2022 04:16:58 +1000
    Received: from ip-1xxxxxxxx-2.compute.internal (10.2.6.109) by
     EX2016-MDB-AN.MYDOMAIN.Hosted (10.2.2.129) with Microsoft SMTP Server
     (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2308.8
     via Frontend Transport; Wed, 4 May 2022 04:17:40 +1000
    Received: from [10.2.6.120] (helo=mail.MYDOMAIN.net)
    	by ip-1xxxxxxxx-2.compute.internal with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
    	(Exim 4.90_1)
    	(envelope-from <lxxxxx@xxxxx.com>)
    	id 1nlx5g-0003dL-JJ
    	for lxxxxx@xxxxx.com; Wed, 04 May 2022 04:17:40 +1000
    Received: from mail.ghfhgdg.com ([85.239.34.13]:33068)
    	by mail.MYDOMAIN.net with esmtps  (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
    	(Exim 4.95)
    	(envelope-from <lxxxxx@xxxxx.com>)
    	id 1nlx5X-00057p-2m
    	for lxxxxx@xxxxx.com;
    	Wed, 04 May 2022 04:17:32 +1000
    Received: from ip63.ip-51-91-202.eu ([51.91.202.63]:53416 helo=galsan.com)
    	by mail.ghfhgdg.com with esmtpsa  (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
    	(Exim 4.95)
    	(envelope-from <lxxxxx@xxxxx.com>)
    	id 1nlx5V-0007v8-Vs
    	for lxxxxx@xxxxx.com;
    	Tue, 03 May 2022 21:17:28 +0300
    X-SASI-Hits: BODYTEXTH_SIZE_3000_MORE 0.000000,
    	BODYTEXTP_SIZE_3000_LESS 0.000000, BODYTEXTP_SIZE_400_LESS 0.000000,
    	BODY_SIZE_10000_PLUS 0.000000, BODY_SIZE_25K_PLUS 0.000000,
    	EXCESSIVE_SUBDOMAINS7 3.000000, FRAUD_ATTACH 0.050000,
    	FROM_NAME_ALLCAPS 0.100000, FROM_RCPT_DOMAIN_NOT_IN_RCVD 0.000000,
    	FROM_SAME_AS_TO_DOMAIN 0.000000, HTML_90_100 0.100000, HTML_95_100 0.100000,
    	IMGSPAM_TABLE_1 0.000000, NO_FUR_HEADER 0.000000, NO_URI_HTTPS 0.000000,
    	OUTBOUND 0.000000, OUTBOUND_SOPHOS 0.000000, SENDER_NO_AUTH 0.000000,
    	SINGLE_HREF_URI_IN_BODY 0.000000, SINGLE_HREF_URI_WITH_EMAIL 0.000000,
    	__ANY_URI 0.000000, __ATTACHMENT_PHRASE 0.000000, __BODY_NO_MAILTO 0.000000,
    	__BULK_NEGATE 0.000000, __CSHC_NS_B_FN_FA 0.000000, __CT 0.000000,
    	__CTYPE_HAS_BOUNDARY 0.000000, __CTYPE_MULTIPART 0.000000,
    	__CTYPE_MULTIPART_ALT 0.000000, __DATA_URL_SCHEME 0.000000,
    	__DATE_TZ_HK 0.000000, __DQ_NEG_DOMAIN 0.000000, __DQ_NEG_HEUR 0.000000,
    	__DQ_NEG_IP 0.000000, __EXCESSIVE_SUBDOMAINS6 0.000000,
    	__EXCESSIVE_SUBDOMAINS7 0.000000, __FAX_BODY 0.000000,
    	__FILESHARE_PHRASE 0.000000, __FRAUD_ANTIABUSE 0.000000,
    	__FROM_DOMAIN_IN_ANY_TO1 0.000000, __FROM_DOMAIN_IN_RCPT 0.000000,
    	__FROM_NAME_NOT_IN_ADDR 0.000000, __FROM_NAME_NOT_IN_BODY 0.000000,
    	__FUR_RDNS_SOPHOS 0.000000, __HAS_FROM 0.000000, __HAS_HTML 0.000000,
    	__HAS_MSGID 0.000000, __HTML_AHREF_TAG 0.000000, __HTML_BAD_END 0.000000,
    	__HTML_TAG_CENTER 0.000000, __HTML_TAG_IMG_X2 0.000000,
    	__HTML_TAG_TABLE 0.000000, __IMGSPAM_TABLE_1 0.000000,
    	__IMG_THEN_TEXT 0.000000, __MIME_HTML 0.000000, __MIME_TEXT_H 0.000000,
    	__MIME_TEXT_H1 0.000000, __MIME_TEXT_H2 0.000000, __MIME_TEXT_P 0.000000,
    	__MIME_TEXT_P1 0.000000, __MIME_TEXT_P2 0.000000, __MIME_VERSION 0.000000,
    	__MULTIPLE_URI_TEXT 0.000000, __OUTBOUND_SOPHOS_FUR 0.000000,
    	__OUTBOUND_SOPHOS_FUR_IP 0.000000, __OUTBOUND_SOPHOS_FUR_RDNS 0.000000,
    	__PHISH_PHRASE10_D 0.000000, __RCPT_DOMAIN_IS_FROM_DOMAIN 0.000000,
    	__SANE_MSGID 0.000000, __SUBJ_ALPHA_END 0.000000, __TAG_EXISTS_HTML 0.000000,
    	__TO_DOMAIN_IN_FROM 0.000000, __TO_DOMAIN_IN_MSGID 0.000000,
    	__TO_MALFORMED_2 0.000000, __TO_NO_NAME 0.000000,
    	__URI_EMAIL_IN_QUERY 0.000000, __URI_IN_BODY 0.000000, __URI_MAILTO 0.000000,
    	__URI_NOT_IMG 0.000000, __URI_NO_PATH 0.000000, __URI_NO_WWW 0.000000,
    	__URI_NS 0.000000, __URI_WITHOUT_PATH 0.000000
    X-SASI-Probability: 30%
    X-SASI-RCODE: 200
    X-SASI-Version: Antispam-Engine: 4.1.4, AntispamData: 2022.5.3.173622
    From: HOA ORDERS <lxxxxx@xxxxx.com>
    To: <lxxxxx@xxxxx.com>
    Subject: Requested HOA Letter
    Date: Wed, 4 May 2022 02:17:27 +0800
    Message-ID: <20220504021727.BFD45D6D250BF3FA@xxxxx.com>
    MIME-Version: 1.0
    Content-Type: multipart/alternative;
    	boundary="----=_NextPart_000_0012_1F95ED89.02DDA1DF"
    X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
    X-AntiAbuse: Primary Hostname - mail.ghfhgdg.com
    X-AntiAbuse: Original Domain - xxxxx.com
    X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
    X-AntiAbuse: Sender Address Domain - xxxxx.com
    X-Get-Message-Sender-Via: mail.ghfhgdg.com: authenticated_id: dennis@ghfhgdg.com
    X-Authenticated-Sender: mail.ghfhgdg.com: dennis@ghfhgdg.com
    X-Source:
    X-Source-Args:
    X-Source-Dir:
    Return-Path: lxxxxx@xxxxx.com
    X-MS-Exchange-Organization-Network-Message-Id: 2be4961d-c269-4b3a-e3f4-08da2d3135da
    X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
    X-MS-Exchange-Organization-AuthSource: EX2016-MDB-AN.MYDOMAIN.Hosted
    X-MS-Exchange-Organization-AuthAs: Anonymous
    X-MS-Exchange-Processed-By-BccFoldering: 15.01.2308.008

  • Ok, I suggest xxxxx.com stands for your domain.

    Which hop is your UTM? mail.MYDOMAIN.net?

    How looks your SPF-Setting in the DNS?

    bye Josef

    BERGMANN engineering & consulting GmbH, Wien/Austria

  • Yes, mail.MYDOMAIN.net is the UTM hop.

    This is what the SPF settings look like:
    v=spf1 mx ip4:13.xx.xx.xx ip4:13.xx.xx.xx ip4:13.xx.xx.xx ip4:13.xx.xx.xx ip4:13.xx.xx.xx include:spf.messagelabs.com include:spf.protection.outlook.com include:spf.smtp2go.com ~all

    Can anyone spot any issues?

Reply
  • Yes, mail.MYDOMAIN.net is the UTM hop.

    This is what the SPF settings look like:
    v=spf1 mx ip4:13.xx.xx.xx ip4:13.xx.xx.xx ip4:13.xx.xx.xx ip4:13.xx.xx.xx ip4:13.xx.xx.xx include:spf.messagelabs.com include:spf.protection.outlook.com include:spf.smtp2go.com ~all

    Can anyone spot any issues?

Children
  • Ok so you use "Softfail" (~all) in your SPF-policy, these will not stop the spoofed mail on the UTM.

    More details see here Sophos UTM: Enable Sender Policy Framework (SPF)

    "... Your SPF record should contain the token "-all" at the end not "~all". This is a common reason why people are not rejecting spoofed mail as expected."

    bye Josef

    BERGMANN engineering & consulting GmbH, Wien/Austria

  • Hi Josef, I know we use "Softfail", but we have "Perform SPF check" turned on and I can see a lot of emails got rejected because of SPF check failed.

    I still think we have is an open relay problem, not an SPF problem.

  • If you don't check your own mail logs after doing the OpenRelay test, you would never really know this.

    PS: and i think SPF soft-fail will pass UTM-Spam filter. (you may check SPF-records from SPF-blocked mails)


    Dirk

    Systema Gesellschaft für angewandte Datentechnik mbH  // Sophos Platinum Partner
    Sophos Solution Partner since 2003
    If a post solves your question, click the 'Verify Answer' link at this post.

  • As said the UTM will not reject when the SPF-policy is set to Softfail, this is documented in the link I posted.

    All the mails which you see rejecting for sure have a Hardfail SPF-policy. Your Domain have a Softfail-policy, so the mails got not rejected. The Feature "Perform SPF check" just enable the check general.

    bye Josef

    BERGMANN engineering & consulting GmbH, Wien/Austria

  • Good morning, Johnny.  You got the answer from both Dirk and Josef.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • Apologies for the late reply.

    Unfortunately, the solutions proposed didn't work, we updated SPF to "hard fail" but it still doesn't stop the phishing emails.

    Here is the email header looks like -

    Received: from EX2016-MDB-AN.xxx.hosted (10.2.4.129) by
     EX2016-MDB-AN.xxx.hosted (10.2.4.129) with Microsoft SMTP Server
     (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2308.8
     via Mailbox Transport; Wed, 20 Jul 2022 14:15:40 +1000
    Received: from EX2016-MDB-AN.xxx.hosted (10.2.4.129) by
     EX2016-MDB-AN.xxx.hosted (10.2.4.129) with Microsoft SMTP Server
     (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
     15.1.2308.8; Wed, 20 Jul 2022 14:15:40 +1000
    Received: from ip-10-2-3-109.ap-xxxx.compute.internal (10.2.5.109) by
     EX2016-MDB-AN.xxx.hosted (10.2.4.129) with Microsoft SMTP Server
     (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2308.8
     via Frontend Transport; Wed, 20 Jul 2022 14:15:40 +1000
    Received: from [10.2.4.120] (helo=mail.xxx.com)
    	by ip-10-2-3-109.ap-southeast-2.compute.internal with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
    	(Exim 4.90_1)
    	(envelope-from <user@xxx.com>)
    	id 1oE17c-0004qV-OG
    	for user@xxx.com; Wed, 20 Jul 2022 14:15:40 +1000
    Received: from [185.222.58.69] (port=62467 helo=xxx.com)
    	by mail.xxx.com with esmtp (Exim 4.95)
    	(envelope-from <user@xxx.com>)
    	id 1oE17W-0001WW-0x
    	for user@xxx.com;
    	Wed, 20 Jul 2022 14:15:34 +1000
    From: xxx.com Server <user@xxx.com>
    To: <user@xxx.com>
    Subject: Three (4) Incoming mails not delivered
    Date: Wed, 20 Jul 2022 06:15:30 +0200
    Message-ID: <20220720061530.C5379167367D62FD@xxx.com>
    MIME-Version: 1.0
    Content-Type: text/html; charset="iso-8859-1"
    Content-Transfer-Encoding: quoted-printable
    Return-Path: user@xxx.com
    X-MS-Exchange-Organization-Network-Message-Id: e0bd540b-123e-4816-8107-08da6a0681e5
    X-MS-Exchange-Organization-AVStamp-Enterprise: 1.0
    X-MS-Exchange-Organization-AuthSource: EX2016-MDB-AN.xxx.hosted
    X-MS-Exchange-Organization-AuthAs: Anonymous
    X-MS-Exchange-Transport-EndToEndLatency: 00:00:00.1880204
    X-MS-Exchange-Processed-By-BccFoldering: 15.01.2308.008

    Received: from [185.222.58.69] (port=62467 helo=xxx.com)
    by mail.xxx.com with esmtp (Exim 4.95)
    (envelope-from <user@xxx.com>)
    id 1oE17W-0001WW-0x
    for user@xxx.com;
    Wed, 20 Jul 2022 14:15:34 +1000

    The first "Received: from [185.222.58.69]" is not in the SPF record, yet it is the IP that the email originated from.

  • Hi,

    send me a PM with the real log.

    bye Josef

    BERGMANN engineering & consulting GmbH, Wien/Austria

  • Josef will help you.  The line we would need to see is the one where the SMTP Proxy receives the email.  That line would be above those you posted.

         Received: from mail-dm6nam10on2109.outbound.protection.outlook.com ([40.107.93.109]:27105 helo=NAM10-DM6-obe.outbound.protection.outlook.com)
             by xxxxx.mediasoftusa.com with esmtps

    The above came from a client at a company that hosts their email with outlook.  40.107.93.109 is included in the SPF record for spf.protection.outlook.com.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • Thank you all, I have sent a pm to Josef.

    We received another phishing attack, the attacker managed to pass the SPF check

     Authentication-Results: wps01.wadax.ne.jp;
    spf=pass (sender IP is 18.119.141.193) smtp.mailfrom=abc@xxx.com smtp.helo=[127.0.0.1]
    Received-SPF: pass (wps01.wadax.ne.jp: connection is authenticated)

    I have no idea how they could they do that? the IP is probably in one of these includes

    include:spf.messagelabs.com include:spf.protection.outlook.com include:spf.smtp2go.com

  • Phishing attacks are rarely stopped by SPF.  Most are done with an account that was hijacked or from a new account at an email provider like Gmail - Google seems to be the email of choice for online criminals.  The best defense against phishing is anti-phishing training for your organization, like Sophos Phish Threat.

    Note that that the content of the From field in an email can be spoofed instead of being the same as the Sender.  This is likely what happened to your coworkers as described in your opening post in this thread.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA