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ATP Alerts Tor Exit Nodes

COMODDORE

Hi All,

I wonder if anyone can help me clarify the following, we start receiving standard ATP alerts for the past month as per bellow, usually im able to investigate this alerts and they either are DNS recursive queries performed by out forwarders on Spam domain emails  received and rejected by the SMTP proxy, or Web sessions hijack attempts trying to redirect traffic to malicious domains, but recently i been baffled by a a recurrent alert as bellow where im not able to make much sense, i parsed the logs for our SMTP proxy that shows traffic to a Tor node from what i can only assume being SMTP connections rejected by the UTM  does anyone have any idea on this ?

2021:10:27-12:50:55 srvutm-1 exim-in[8916]: 2021-10-27 12:50:55 SMTP connection from [185.220.100.254]:31034 (TCP/IP connection count = 4)
2021:10:27-12:50:57 srvutm-1 exim-in[23862]: 2021-10-27 12:50:57 TLS error on connection from tor-exit-3.zbau.f3netze.de [185.220.100.254]:31034 SSL_accept: TCP connection closed by peer
2021:10:27-12:50:57 srvutm-1 exim-in[8916]: 2021-10-27 12:50:57 SMTP connection from [185.220.100.254]:32560 (TCP/IP connection count = 4)
2021:10:27-12:51:01 srvutm-1 exim-in[23909]: 2021-10-27 12:51:01 TLS error on connection from tor-exit-3.zbau.f3netze.de [185.220.100.254]:32560 SSL_accept: TCP connection closed by peer
2021:10:27-17:12:32 srvutm-1 exim-in[8916]: 2021-10-27 17:12:32 SMTP connection from [185.220.100.254]:14154 (TCP/IP connection count = 2)
2021:10:27-17:12:33 srvutm-1 exim-in[5631]: 2021-10-27 17:12:33 TLS error on connection from tor-exit-3.zbau.f3netze.de [185.220.100.254]:14154 SSL_accept: TCP connection closed by peer
2021:10:29-03:34:26 srvutm-1 exim-in[6731]: 2021-10-29 03:34:26 SMTP connection from [185.220.100.254]:22392 (TCP/IP connection count = 1)
2021:10:29-03:34:28 srvutm-1 exim-in[18207]: 2021-10-29 03:34:28 TLS error on connection from tor-exit-3.zbau.f3netze.de [185.220.100.254]:22392 SSL_accept: TCP connection closed by peer

A threat has been detected in your network The source IP/host listed below was found to communicate with a potentially malicious site outside your company.

Advanced Threat ProtectionDetails
Total Events: 2
User/Host Threat Name Destination Events Origin
1 192.168.7.250 C2/Generic-A 185.220.100.254 
2 192.168.7.250 C2/Generic-A 185.220.100.254 



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Parents
  • 0

    Hi again,

    has anyone here of the people who receive the ATP alerts found an actual way to get rid of these specific ATP alerts? We still receive the alerts multiple times per week. Still from the same subnet. From my understanding there is exactly nothing to do against these dns requests. We have put the subnet into a blackhole NAT as suggested by BAlfson. Still no change and the alerts are getting quite annoying at this point. Like; someone from the subnet just has to ping us and we receive an alert. There has to be a solution for this. Or do you guys all just live with it at this point?

    regards

Reply
  • 0

    Hi again,

    has anyone here of the people who receive the ATP alerts found an actual way to get rid of these specific ATP alerts? We still receive the alerts multiple times per week. Still from the same subnet. From my understanding there is exactly nothing to do against these dns requests. We have put the subnet into a blackhole NAT as suggested by BAlfson. Still no change and the alerts are getting quite annoying at this point. Like; someone from the subnet just has to ping us and we receive an alert. There has to be a solution for this. Or do you guys all just live with it at this point?

    regards

Children
  • +1 in reply to HNNG

    still receiving these messages as well. But we didn´t do something so far. This week or next, we´ll change the DNS settings as the forwarders are pointing to internal DNS´s at the moment. 
    We assume this will solve the problem.

    Seems like these messages are generate, because a SMTP request is coming from tor, UTM checks it and forwards a dns request to internal, to verify. DNS Servers can not verify itself, so it asks its forwarders (ISP dns´s) and thats the point when the ATP message is raised.

    When the UTM´s forwarders are the ISPs directly, this alert shouldn´t be raisedanymore.

    At least this is what we think/hope/believe and our sophos partner as well. Support is still not helpfull.

  • 0 in reply to HNNG

    ´Hey,

    my way to work around it was to treat these as false positive and put these handful of host onto the threat exception list:

    Advanced Threat Protection > Threat Exceptions:
    185.220.100.254
    185.220.100.243
    185.220.100.244
    185.220.101.35

    I can live with that, especially because I fear that, after a while, I won't look at the alerts anymore discarding them as "again only a dns tor issue again".

    Cheers,
        Marius
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