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Problem, snort block google server

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  • C
    claudio.gallix
    last edited by Sep 28, 2020, 6:32 PM

    Good evening, this is my first post.
    I start with a question.
    Since a week, snort blocks google servers. All google apps are blocked, drive, classroom, calendar ecc.
    I have not made any changes.
    What could be the problem?

    thanks a lot to everyone.

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    • S
      serbus
      last edited by Sep 28, 2020, 7:50 PM

      Hello!

      What do the snort alert log lines from the google servers being blocked look like?

      John

      Lex parsimoniae

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      • C
        claudio.gallix
        last edited by Sep 29, 2020, 9:06 AM

        In blocked there are

        Cattura.PNG

        In alerts

        Cattura.PNG
        Cattura1.PNG

        etc etc

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        • B
          bmeeks
          last edited by bmeeks Sep 29, 2020, 2:15 PM Sep 29, 2020, 12:22 PM

          The Portscan preprocessor in Snort can be trigger happy. It is simply incorrectly interpreting some rapid-fire communications as "port scans". You can turn the sensitivity of the preprocessor down to "low", but I would recommend disabling it and the associated rules altogether on a home network.

          Or you can simply disable that particular UDP rule by clicking the red X under the GID:SID column. I suggest you try that first.

          Tuning an IDS/IPS is a continual job. You don't just install the package, enable some rules and let it run. Doing that will lead to nuisance blocks from false positives. You must tune the setup for your particular network traffic. That means disabling or suppressing certain rules that trigger on non-malicious traffic in your network.

          I don't mean to be harsh, but the way you asked your question in this thread and the fact you had no idea why you were getting blocks indicates you are very new to IDS/IPS administration. You really need to run Snort in IDS mode (non-blocking for several weeks) to get a feel for alerts that happen in your network. Then research each alert to figure out why it occurred and if it is a false positive. Then you disable those rules which fire on false positives. After you get the system tuned to the point where you are getting very few alerts, then you enable blocking.

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          • C
            claudio.gallix
            last edited by Sep 29, 2020, 12:42 PM

            thankyou i try.

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