[Bro-Dev] [JIRA] (BIT-1427) rare SSH successful login heuristic FPs

Vern Paxson (JIRA) jira at bro-tracker.atlassian.net
Sun Jun 21 09:20:00 PDT 2015

     [ https://bro-tracker.atlassian.net/browse/BIT-1427?focusedWorklogId=10100&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-10100 ]

Vern Paxson logged work on BIT-1427:

                Author: Vern Paxson
            Created on: 21/Jun/15 11:19 AM
            Start Date: 21/Jun/15 11:19 AM
    Worklog Time Spent: 5 minutes 
      Work Description: Already presumed fixed in 2.4.

Issue Time Tracking

            Worklog Id:     (was: 10100)
            Time Spent: 5 minutes
    Remaining Estimate: 0 minutes

> rare SSH successful login heuristic FPs
> ---------------------------------------
>                 Key: BIT-1427
>                 URL: https://bro-tracker.atlassian.net/browse/BIT-1427
>             Project: Bro Issue Tracker
>          Issue Type: Problem
>          Components: Bro
>    Affects Versions: 2.3
>            Reporter: Vern Paxson
>             Fix For: 2.4
>          Time Spent: 5 minutes
>  Remaining Estimate: 0 minutes
> During a bruteforce attack that made 27M attempted logins, 2 were flagged as successful by one instance of Bro monitoring the traffic, but not by another running an identical config on the same traffic stream.  I wasn't able to reproduce the FPs from bulk traces of the event.  Both instances were associated with two Weirds, "SYN_after_close" and "excessive_data_without_further_acks" that were otherwise quite rare in the traffic.  This suggests that there's a flaw in the heuristic whereby it's analyzing traffic streams that have confused state.  Perhaps an adequate fix is to track whether a given flow has experienced those Weirds, and if so, don't apply the heuristic to it.

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