Extremely persistent sex/make money spam with very little text in the body

[Sebastian Arcus <s....@open-t.co.uk>]

I have this one email account receiving, for more than a year, a very 
specific type of spam which I find very difficult to block:

1. The messages are all kept very short, generally below 20 words - I 
assume so that Bayes is less efficient at classifying them?

2. Although they are all invitations to sex, or making money - they are 
phrased differently every time and use different words - so Bayes scores 
are consistently low.

3. They come from servers all around the world - possibly compromised, 
or maybe quickly setup and taken down - so they are usually not flagged 
by blacklists

4. Pyzor tends to flag most of them up though.

5. In most cases, DKIM is correct, SPF is fine, and the headers are all 
correct - so they don't hit any other rules.

6. The links they include in the body of the email are almost never 
flagged up either by Clam or Spamassassin - and they point to a 
different domain in every single message.

The bizarre thing is that I only see them coming to this one particular 
email account, at a single domain of all the ones I administer. Based on 
the above whoever sends them really know what they are doing, and must 
have significant resources at their disposal - but I still have no idea 
why they only hit this particular email address. I can only assume that 
greylisting wouldn't help much, as they seem to arrive from properly 
configured smpt servers, which would retry like any other regular smtp 
server and bypass greylisting. Has anybody else seen these, and is there 
anything else that I could try to block them?

Re: Extremely persistent sex/make money spam with very little text in the body

[Sebastian Arcus <s....@open-t.co.uk>]

On 07/03/18 11:25, Leandro wrote:
> 2018-03-07 5:52 GMT-03:00 Sebastian Arcus <s.arcus@open-t.co.uk 
> <ma...@open-t.co.uk>>:
> 
> 
>     6. The links they include in the body of the email are almost never
>     flagged up either by Clam or Spamassassin - and they point to a
>     different domain in every single message.
> 
> 
> Although they use multiple domains in the URLs at body, many of these 
> URLs are addressed to the same IPv4/IPv6 address or IP ranges, that is 
> just one shared web server or a group of shared web servers of the spammer.
> 
> The key to solving this problem is that you all start to cross the data 
> and start scoring the URL host IP, that is the exact fiscal place they 
> want to you visit even fired by many hacked mail servers at world and 
> many distinct domains. The mail services and domains are very disperse 
> but the web servers are very concentrated.

As far as I can tell, the URL's in the spam I see point to php scripts 
on various compromised servers - which, maybe, further redirect to the 
final payment servers. But thank you for the suggestion - I will keep an 
eye on it.

Re: Extremely persistent sex/make money spam with very little text in the body

[Leandro <le...@spfbl.net>]

2018-03-07 5:52 GMT-03:00 Sebastian Arcus <s....@open-t.co.uk>:

>
> 6. The links they include in the body of the email are almost never
> flagged up either by Clam or Spamassassin - and they point to a different
> domain in every single message.
>

Although they use multiple domains in the URLs at body, many of these URLs
are addressed to the same IPv4/IPv6 address or IP ranges, that is just one
shared web server or a group of shared web servers of the spammer.

The key to solving this problem is that you all start to cross the data and
start scoring the URL host IP, that is the exact fiscal place they want to
you visit even fired by many hacked mail servers at world and many distinct
domains. The mail services and domains are very disperse but the web
servers are very concentrated.

We are doing this technique here and the problem has been mitigated to our
customers.


>
> The bizarre thing is that I only see them coming to this one particular
> email account, at a single domain of all the ones I administer. Based on
> the above whoever sends them really know what they are doing, and must have
> significant resources at their disposal - but I still have no idea why they
> only hit this particular email address. I can only assume that greylisting
> wouldn't help much, as they seem to arrive from properly configured smpt
> servers, which would retry like any other regular smtp server and bypass
> greylisting. Has anybody else seen these, and is there anything else that I
> could try to block them?
>

Re: Extremely persistent sex/make money spam with very little text in the body

[Sebastian Arcus <s....@open-t.co.uk>]

On 07/03/18 09:08, Daniele Duca wrote:
> On 07/03/2018 09:52, Sebastian Arcus wrote:
> 
>> I have this one email account receiving, for more than a year, a very 
>> specific type of spam which I find very difficult to block:
>>
>> 1. The messages are all kept very short, generally below 20 words - I 
>> assume so that Bayes is less efficient at classifying them?
>>
>> 2. Although they are all invitations to sex, or making money - they 
>> are phrased differently every time and use different words - so Bayes 
>> scores are consistently low.
> <snip>
> 
> Hi Sebastian,
> 
> I perfectly know what type of email you are talking about, I've seen 
> them written at least in italian, english and spanish. If you click the 
> link you are being redirected to shady dating websites or 
> bitcoin/investment scams sites (at least in my experience).
> 
> Since I get the majority of these emails in italian, I've written a meta 
> rule that takes in account:
> 
> - Common mispelled words/phrases
> - Body lines must be < 5
> - The common pattern in all the urls. Take a close look at them, there 
> IS a pattern, not writing it here for obvious reasons :)

Thank you so much for that! The emails I see don't usually have spelling 
mistakes, but you are right, it seems that the url is the way to go. 
I've been looking for patters in the headers and source servers all 
along - it never crossed my mind to check the body! Thanks again

Re: Extremely persistent sex/make money spam with very little text in the body

[Daniele Duca <du...@staff.spin.it>]

On 07/03/2018 17:32, Jakob Curdes wrote:
>
>>
>> Since I get the majority of these emails in italian, I've written a 
>> meta rule that takes in account:
> Hello Duca, would you share this rule with us? I would be interested 
> in looking at the resulst, as we also have lots of these messages here.
> JC
Hi,

I believe my rule wouldn't be as useful for you because a part of it is 
related to mispelled italian words (i believe they sloppily translated 
from english)

However, I'll drop an email to you offlist with the other relevant parts 
to avoid eventual spammers lurking here ;)

Daniele

Re: Extremely persistent sex/make money spam with very little text in the body

[Jakob Curdes <jc...@info-systems.de>]

>
> Since I get the majority of these emails in italian, I've written a meta rule that takes in account:
Hello Duca, would you share this rule with us? I would be interested in looking at the resulst, as 
we also have lots of these messages here.
JC

Re: Extremely persistent sex/make money spam with very little text in the body

[Daniele Duca <du...@staff.spin.it>]

On 07/03/2018 09:52, Sebastian Arcus wrote:

> I have this one email account receiving, for more than a year, a very 
> specific type of spam which I find very difficult to block:
>
> 1. The messages are all kept very short, generally below 20 words - I 
> assume so that Bayes is less efficient at classifying them?
>
> 2. Although they are all invitations to sex, or making money - they 
> are phrased differently every time and use different words - so Bayes 
> scores are consistently low.
<snip>

Hi Sebastian,

I perfectly know what type of email you are talking about, I've seen 
them written at least in italian, english and spanish. If you click the 
link you are being redirected to shady dating websites or 
bitcoin/investment scams sites (at least in my experience).

Since I get the majority of these emails in italian, I've written a meta 
rule that takes in account:

- Common mispelled words/phrases
- Body lines must be < 5
- The common pattern in all the urls. Take a close look at them, there 
IS a pattern, not writing it here for obvious reasons :)

If all these conditions are matched the email is flagged. So far (about 
6 months), no complaints. If you have only one address that receives 
these emails I'd add a test to see if the recipient is that specific one 
for more precision

Hope it helps
Daniele