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SMTP being hijacked - trying to block sender

steagle
Looks like over the weekend we got hijacked and now I have spammers from Italy using our SMTP relay to send thousands of emails. I have added their domains to the sender blacklist filter and the expression filter, but the emails continue to pour through. Obviously, I'm not using the right tool to stop them. I've got a list of the domains they're using - does anyone know how I can block these guys? Thanks!

edit: Also realized this could be a malware intrusion on one of our workstations - we are currently scanning all machines with Malwarebytes to see if we can find the culprit. Just in case this is not the issue and we indeed have been hijacked, any tips for dealing with this would be highly appreciated. 
____

ASG220
Firmware 7.501
Pattern Version 22662


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  • 0
    That's a UK IP address that's part of a /28 public subnet, so the ISP should be able to alert their customer to the apparent fact that they have an infection: abuse@as29550.net.  Include a large enough portion of your log to demonstrate that this was an attack.

    Is there a reason you need to allow authentication traffic originating from outside your network?  Would requiring remote mail clients to use a VPN from company-certified laptops suffice?  Or, could you require remote mail users to access via an internal web-based application similar to Outlook Web Access?

    Cheers - Bob
     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
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  • 0
    That's a UK IP address that's part of a /28 public subnet, so the ISP should be able to alert their customer to the apparent fact that they have an infection: abuse@as29550.net.  Include a large enough portion of your log to demonstrate that this was an attack.

    Is there a reason you need to allow authentication traffic originating from outside your network?  Would requiring remote mail clients to use a VPN from company-certified laptops suffice?  Or, could you require remote mail users to access via an internal web-based application similar to Outlook Web Access?

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