another one got through. why, how?!

Riesling.Dry

Renowned Member
Jul 17, 2014
90
7
73
User got this SPAM over the weekend. Countless, basically identical mails got through and we had similar cases in the past.
He has catchall email for this Domain and X-Original-To went to random addresses @his.Domain, while the To:-address is on a totally unrelated Domain.
How did the SPAMMERs manage to bypass PMG's checks and how can further similar incidents be avoided?
Needless to say, that the SPAMMERs Domain and the content of the emails change every time, so blacklisting them - which was of course done, yet merely after user reported - won't probably do much...

Cheers,
~R.

Return-Path: <ucxepfs@azimuters.gen.tr> X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on [ destination.host ] X-Spam-Level: X-Spam-Status: No, score=-3.2 required=5.0 tests=BAYES_00,HTML_FONT_SIZE_LARGE, HTML_IMAGE_ONLY_24,HTML_IMAGE_RATIO_04,HTML_MESSAGE,PYZOR_CHECK, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_SOFTFAIL,T_SCC_BODY_TEXT_LINE, T_TVD_MIME_EPI autolearn=ham autolearn_force=no version=3.4.2 X-Original-To: 7gbamc5fwb3gz7h@[ user domain redacted for privacy ] Delivered-To: default@[ destination.host ] Received: from [ pmg.host ] ([ pmg.host ] [ pmg IP ]) by [ destination.host ] (Postfix) with ESMTP id 07EA570FB0; Mon, 20 Jun 2022 00:46:26 +0200 (CEST) Received: from [ pmg.host ] (localhost [127.0.0.1]) by [ pmg.host ] (Proxmox) with ESMTP id 5E18D60FD3; Sun, 19 Jun 2022 23:39:52 +0200 (CEST) Received-SPF: pass (azimuters.gen.tr: 46.19.137.136 is authorized to use 'ucxepfs@azimuters.gen.tr' in 'mfrom' identity (mechanism 'a' matched)) receiver=[ pmg.host ]; identity=mailfrom; envelope-from="ucxepfs@azimuters.gen.tr"; helo=mail.azimuters.gen.tr; client-ip=46.19.137.136 Received-SPF: pass (azimuters.gen.tr: 46.19.137.136 is authorized to use 'ucxepfs@azimuters.gen.tr' in 'mfrom' identity (mechanism 'a' matched)) receiver=[ pmg.host ]; identity=mailfrom; envelope-from="ucxepfs@azimuters.gen.tr"; helo=mail.azimuters.gen.tr; client-ip=46.19.137.136 Received: from mail.azimuters.gen.tr (mail.azimuters.gen.tr [46.19.137.136]) by [ pmg.host ] (Proxmox) with ESMTP id EB6FE6002D; Sun, 19 Jun 2022 23:39:50 +0200 (CEST) Received: from azimuters.gen.tr (rel.tetarox.site [2.56.88.81]) by mail.azimuters.gen.tr (Postfix) with ESMTPA id 332CC7F19; Sun, 19 Jun 2022 23:48:12 +0300 (EEST) Message-ID: <53646257401831364774715016820331@azimuters.gen.tr> From: "CARDIOXIL" <ucxepfs@azimuters.gen.tr> To: <comercial@hipocrate2002serv.ro> Subject: =?utf-8?B?MSBsdW7EgyBkZSBhZG1pbmlzdHJhcmUgQ2FyZGlveGlsIC0gZSBjYSDImWkgY3VtIHRlLWFpIG5hyJl0ZSBkaW4gbm91?= Date: Sun, 19 Jun 2022 23:48:22 +0300 MIME-Version: 1.0 Content-Type: multipart/related; type="multipart/alternative"; boundary="----=_NextPart_000_0006_01D88435.36FD4250" This is a multi-part message in MIME format. ------=_NextPart_000_0006_01D88435.36FD4250 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0007_01D88435.36FD4250" ------=_NextPart_000_0007_01D88435.36FD4250 Content-Type: text/plain; charset="windows-1251" Content-Transfer-Encoding: quoted-printable =0D=0A=0D=0A=0D=0A=0D=0ACardioxil este o comoar&#259; de extracte= medicinale care func&#539;ioneaz&#259; =0D=0Aarmonios pentru a v= &#259; men&#539;ine vasele de s&#226;nge curate &#537;i =0D=0Afer= me.=0D=0A =0D=0ACondi&#539;ii pentru =0D=0Aachizi&#539;ionarea Ca= rdioxil &#238;n cadrul =0D=0Aprogramului:=0D=0A =0D=0AComanda&#53= 9;i =0D=0ACardioxil pentru uz =0D=0Apersonal.=0D=0AComanda&#539;i= un produs pentru dvs., familie =0D=0Asau prieteni. 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Setup DNSBL, mail filter and spamassassin should help to improve spam detection.
 
you should be able to block all mails coming from domains without PTR's and this solves the issues 99% of the time since spam mails arent usually legitimate.

just know that you might block some legitimate mails if you do this.

every ISP with a mail server usually choose this option :) .

another solution could be adding a blacklist, you can find them pretty easyly by searching for it on google there is quite a bit.
 
From your mail header, there is no X-SPAM-LEVEL info. Did you enable the default modify header mail rule?
You still did not list down what mail filter rule that you have setup to filter the spam.
 
you should be able to block all mails coming from domains without PTR's and this solves the issues 99% of the time since spam mails arent usually legitimate.
Thanks, but these bastards apparently do have a perfect PTR, so this approach wouldn't have blocked them, I guess? :)
Code:
~ % host 46.19.137.136
136.137.19.46.in-addr.arpa domain name pointer mail.azimuters.gen.tr.
 
From your mail header, there is no X-SPAM-LEVEL info.
The 'X-Spam-Level:' header is empty when the score is too low (chicken-egg-problem?)
...and in order to find out, WHY it is too low (and consequently the SPAM got through) I started this thread. :)
Did you enable the default modify header mail rule?
Not sure. Where/how is this done? Isn't that part of PMG by default?
You still did not list down what mail filter rule that you have setup to filter the spam.
As I said, we have set up nothing beyond what is "factory default" and "built-in" w. PMG and edited resolv.conf to be able to use URIBL.
But considering we do not know what SPAM will come, it is difficult to somehow "precautionary" set rules. Yes, the ones you mentioned in your post do make sense but wouldn't have caught this one either.

To be clear: PMG does a brilliant almost perfect job, yet there is the occasional one that manages to get through - so why not talk about it w. the option of going from almost perfect to perfect? :)

That's why I ask: how/why did this one get through? :)
 
Thanks, but these bastards apparently do have a perfect PTR, so this approach wouldn't have blocked them, I guess? :)
Code:
~ % host 46.19.137.136
136.137.19.46.in-addr.arpa domain name pointer mail.azimuters.gen.tr.
i dont know where you got that IP from i tried some of the domain names on your picture and some of them didnt have any ptr

anyways this could help you filter away a great deal of the mails i believe. i hope you find a good solution.

have a great day.

kind regards :)
 
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