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Block spoofing emails

Johnny Long

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

  • in reply to JosefBergmann

    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.

  • in reply to Johnny Long

    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.

  • in reply to dirkkotte

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

  • in reply to dirkkotte

    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...

  • in reply to Johnny Long

    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.

  • in reply to Johnny Long

    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:

    Johnny Long said:
    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

  • in reply to JosefBergmann

    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

  • in reply to Johnny Long

    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

  • in reply to JosefBergmann

    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?

  • in reply to dirkkotte

    The results show as

    SendSMTPCommand: You hung up on us after we connected. Please whitelist us. (connection lost)

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