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Next: Replacing Packets with Snort Up: Inline Mode Previous: Snort Inline Rule Application   Contents


New STREAM4 Options for Use with Snort Inline

When using Snort Inline, you can use two additional stream4 options:

  • enforce_state drop

    Adding drop to the enforce_state option causes Snort to drop TCP packets that are not associated with an existing TCP session, and that are not valid TCP initiators.

  • midstream_drop_alerts (no arguments)

    By default, when running in inline mode, Snort will silently drop any packets that are matched against a drop rule and considered to be part of a midstream session, instead of logging the alert as usual. This is to mitigate stick/snot type attacks when the user hasn't enabled the enforce_state option. If you want to log these drops, enable this option. Note that by enabling this option, you have opened yourself up to stick/snot-type attacks if you haven't also used the enforce_state option.

  • disable_session_blocking (no arguments)

    By default, when running in inline mode, Snort will block all traffic on a TCP session after it is told to drop a non-stateless packet on that session. Enable this option if you don't want Snort to exhibit this default behavior.

For more information about Stream4, see Section 2.1.2.

next up previous contents
Next: Replacing Packets with Snort Up: Inline Mode Previous: Snort Inline Rule Application   Contents
Steven Sturges 2008-04-01
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