Solved

Block cyrillic emails in sendmail

Posted on 2009-07-13
3
882 Views
Last Modified: 2013-12-18
Hi,
I have a linux mailserver (CentOS 5.3) with sendmail, I use DNS blacklisting for filtering spam and clamav-milter for viruses. The level of spam is ok with the exception of a few users that receive around 50-100 spam messages/day and all of them in koi8-r encoding (it's cyrillic characters). I need a simple method of blocking or rejecting emails written in cyrillic characters if possible without applying other antispam rules.

Thank you
0
Comment
Question by:aligigi
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
3 Comments
 
LVL 26

Accepted Solution

by:
jar3817 earned 500 total points
ID: 24961430
Without applying other antispam rules? I don't think so. The only thing I can think of is to use a milter like mimedefang (http://mimedefang.org) and test for the encoding of the body in the filter() section.

This site has an example using the subject instead of the body:
http://lists.roaringpenguin.com/pipermail/mimedefang/2009-April/034698.html

This is not for the faint-of-heart and you really need to know some perl, or be able to figure it out.
0
 
LVL 76

Expert Comment

by:Alan Hardisty
ID: 25374021
Not sure about how to do this with sendmail, but if you had Vamsoft ORF (www.vamsoft.com), then you could do this easily.  I use this amongst it's other features and so far in 19 days, have had Zero spam.
It is very well priced too and I am now recommending this to all my customers.
0
 
LVL 3

Author Comment

by:aligigi
ID: 25435650
Hi,
I finally resolved it, I tried simpler solutions, none worked so in the end I used mimedefang. I installed mimedefang using yum, I added the following line to sendmail.mc:
INPUT_MAIL_FILTER(`mimedefang', `S=unix:/var/spool/MIMEDefang/mimedefang.sock, F=T, T=C:30m;S:30m;R:30m;E:30m')
and I added this to mimedefang-filte in the filter procedurer:
    $head = $entity->head;
    $charset = $head->mime_attr("content-type.charset");
    if (defined($charset)) {
      $charset =~ tr/A-Z/a-z/;
      if ($charset eq "koi8-r" or
          $charset eq "euc-kr" or
          $charset eq "koi8-u" or
          $charset eq "3deu-kr" or
          $charset eq "windows-1251") {
          syslog('alert',"MIMEDefang rejected an E-Mail using charset $charset");
         
          return action_bounce("CONTENT VIOLATION: Mail using character set $charset not accepted here");
          }
    }
I had some problems with mimedefang not finding the antivirus (I use clamav) so I commented out that part of the code since I use clamav-milter directly in sendmail.mc.
Thanks for the help.
0

Featured Post

Ready to trade in that old firewall?

Whether you need to trade-up to a shiny new Firebox or just ready to upgrade from whatever appliance you're using now, WatchGuard has the right appliance for you! Find your perfect Firebox today with appliance sizing tool!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Pop culture is prime bait for hackers seeking to infect user’s computers and mobile devices with malicious malware. Hackers know exactly what the latest trends are online and know how to use them to their advantage.
As cyber crime continues to grow in both numbers and sophistication, a troubling trend of optimization has emerged over the last year.
Familiarize people with the process of retrieving data from SQL Server using an Access pass-thru query. Microsoft Access is a very powerful client/server development tool. One of the ways that you can retrieve data from a SQL Server is by using a pa…
In this video we show how to create a User Mailbox in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Recipients >> Mailb…
Suggested Courses

635 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question