[Oisf-users] Discrepancies in Snort and Suricata alerts
David Wharton
oisf at davidwharton.us
Wed Oct 3 20:36:19 UTC 2018
Are you sure Suricata is seeing the exact same traffic as Snort? And
processing it? Perhaps it never gets processed because of checksum
offloading/invalid checksums. At the risk of sounding obvious, if Snort
(or Bro or a WAF or a proxy or whatever) is blocking it before Suricata
sees it, then the Suricata rule will never alert.
Are your variables set the same (e.g. $HOME_NET, $EXTERNAL_NET)? Are you
running any IP reputation rules/lists that may be blocking (that IP and
host have been known bad for many years)?
Are you sure you are reading the Suricata alerts correctly? Perhaps they
are being sent somewhere you aren't expecting and/or getting filtered
somewhere.
Without a pcap from the Suricata box and Suricata config, it is going to
be hard to say what the cause of your issue is but likely the Snort and
Suricata boxes aren't seeing the same traffic.
-David
On 10/03/2018 09:27 AM, fatema bannatwala wrote:
> Yet another example where no alerts fired in Suricata but in Snort for
> legit bad traffic for "Andromeda" Trojan.
>
> Both the suri and snort signatures for sid:2809682 are same, and yet
> only snort triggered the alert for an outbound POST request to a
> domain related to Andromeda Trojan.
> Bro detected those connections as http, hence the application should
> be recognized by Suricata as http.
>
> Bro http log for the connection that triggered snort alert:
> 10/2/18 7:06:46.734 PM CGOaPc2Kyn0xd3eGkd 128.x.x.x 58299
> 184.105.192.2 80 1 POST atomictrivia.ru
> <http://atomictrivia.ru> /atomic.php - 1.1 Mozilla/4.0 64 0 200 OK - -
> (empty) - - - FUR4T54aQNbHsxbG84
>
> Snort alert for the same:
> Oct 2 19:06:47 snort[3664]: [1:2809682:3] ETPRO TROJAN
> Andromeda/Gamarue Checkin [Classification: A Network Trojan was
> Detected] [Priority: 1]: {TCP} 128.x.x.x:58299 -> 184.105.192.2:80
> <http://184.105.192.2:80>
>
> No Suricata alerts fired for the same.
>
> The notification of this activity was sent by a third party to us
> today, hence we are sure that the host is compromised as it was trying
> to resolve Andromeda domains.
>
> I can't capture the pcap for the traffic that triggers snort alerts
> but not Suri, as it is sporadic, and only couple of minutes of traffic
> capture results in gigs of traffic, hence I can't just keep running
> pcap capture for a long period of time on the sensors.
> If I can't figure out what is going on with Suri not firing the
> alerts, then we just might have to drop Suricata deployment in prod
> and keep working with Snort.
>
> Any pointers/suggestions?
>
> Thanks,
> Fatema.
> Event
> Actions<https://setter.nss.udel.edu:8443/en-US/app/search/search?q=search%20index%3Dmalware%20128.4.73.143&sid=1538571855.42311&display.page.search.mode=smart&dispatch.sample_ratio=1&earliest=-24h%40h&latest=now#>
>
> On Tue, Sep 25, 2018 at 12:05 PM fatema bannatwala
> <fatema.bannatwala at gmail.com <mailto:fatema.bannatwala at gmail.com>> wrote:
>
> I tried to capture some traffic, but those pcaps aren't triggering
> any alerts in both snort and suricata, have to work on getting
> some pcap with some traffic that would be malicious and could
> trigger alerts.
> Meanwhile, was looking into the alerts that were triggered in
> Snort and not in Suricata for last 15 minutes on live servers, and
> did the following analysis:
>
> Example of few alerts triggered in snort but not in suricata: sid:
> 2022813, 2008974, 2009714
> when I looked at the above alert rules defined in ET ruleset for
> snort and ET ruleset for suricata,
> the only major difference found is in the protocol defined in both
> alerts, i.e. :
>
> suricata alert 2022813 definition:
> alert *http* $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE
> SearchProtect PUA User-Agent Observed";
> flow:established,to_server; content:"SearchProtect|3b|";
> depth:14; http_user_agent;
> reference:md5,34e2350c2ed6a9a9e9d444102ae4dd87;
> classtype:trojan-activity; sid:2022813; rev:2; metadata:created_at
> 2016_05_17, updated_at 2016_05_17;)
>
> snort alert 2022813 definition:
> alert *tcp* $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"ET
> MALWARE SearchProtect PUA User-Agent Observed";
> flow:established,to_server; content:"User-Agent|3a
> 20|SearchProtect|3b|";
> fast_pattern; http_header;
> reference:md5,34e2350c2ed6a9a9e9d444102ae4dd87;
> classtype:trojan-activity; sid:2022813; rev:1; metadata:created_at
> 2016_05_17, updated_at 2016_05_17;)
>
> And from snort alert logs, the packet content that triggered that
> 2022813 alert:
>
> [1:2022813:1] ET MALWARE SearchProtect PUA User-Agent Observed
> 2018-09-25 11:09:39.337000-04:00 128.164.63.89:51872
> <http://128.164.63.89:51872> -> 54.243.209.194:80
> <http://54.243.209.194:80>
> TCP: Data Triggering Snort Rule: POST / HTTP/1.1::~~Content-Type:
> application/json::~~Accept: */*::~~User-Agent:
> SearchProtect;3.0.50.0;Microsoft Windows 7
> Enterprise;SPC0AFF85F-9E31-44AC-8E1C-61C39CDE89DC::~~Host:
> sp-alive-msg.databssint.com::~~Content-Length: 2157::~~Connection:
> Keep-Alive::~~Cache-Control: no-cache::~~::~~
> [Xref => md5 34e2350c2ed6a9a9e9d444102ae4dd87]
>
> Hence, looking at the contents of the above data triggering log,
> looks like it matches the Suricata rule signature as well, except
> not sure if the protocol detected was actually http or not, and
> hence Suricata alert might not have trigged for the same content.
> Other alerts that weren't triggered in Suricata were also having
> "http" in place of "tcp" in the rule signatures, when compared
> with snort rule signatures. Hence my guess is Suricata isn't able
> to detect http protocol for the same traffic and hence not
> triggering the alerts.
>
> Thanks,
> Fatema.
>
>
> On Tue, Sep 25, 2018 at 12:13 AM Michał Purzyński
> <michalpurzynski1 at gmail.com <mailto:michalpurzynski1 at gmail.com>>
> wrote:
>
> It would be really useful to have some data we could work on.
> You can always share pcaps with developers only, subject to
> your company's policy.
>
> One more thing you could do without sharing traffic is to
> verify if these cases when snort matches a signature A and
> Suricata does not, it is a false positive or a true positive.
>
> That would be a great start.
>
>
> On Mon, Sep 24, 2018 at 2:59 PM fatema bannatwala
> <fatema.bannatwala at gmail.com
> <mailto:fatema.bannatwala at gmail.com>> wrote:
>
> Hmm, makes sense, was just curious to know what happens
> when snort ruleset was fed to Suricata,
> and to produce a baseline for the initial test environment
> to see if the important alerts are not missed by Suricata
> once deployed in prod.
> Hence was trying to keep the rulesets same for both for an
> even comparison..
>
> Thanks!
> Fatema.
>
> On Mon, Sep 24, 2018 at 4:29 PM Michael Shirk
> <shirkdog.bsd at gmail.com <mailto:shirkdog.bsd at gmail.com>>
> wrote:
>
> The issue is that the engines are different, so Snort
> signatures from
> VRT/Talos, even ET-Pro written for the Snort detection
> engine are only
> tested with Snort. There was a good presentation by
> Dave Wharton at
> SuriCon 2016 about the subtle differences that can
> cause signatures
> written for either engine to not work in the other.
> Digging into the
> specifics of a signature that works in Snort but does
> not work in
> Suricata may highlight a similar issue.
>
> At least from what I have seen, similar to the issue
> you had with
> pulledpork using a Snort signature set with a Suricata
> signature set,
> I believe the user base selects one detection engine
> over the other.
> The community will send emails with new detections
> that can end up in
> the emerging threats signatures, as well as the
> community based Snort
> rules, but specific to one of the engines.
> On Mon, Sep 24, 2018 at 4:18 PM fatema bannatwala
> <fatema.bannatwala at gmail.com
> <mailto:fatema.bannatwala at gmail.com>> wrote:
> >
> > Hmm, don't want to start Suricata in IPS mode, as
> it's configured to sniff traffic through a tap and
> should really be running as an IDS.
> > Not sure if the triggering of alerts would depend on
> mode though, but I might be wrong..
> >
> > On Mon, Sep 24, 2018 at 3:41 PM Albert Whale
> <Albert.Whale at it-security-inc.com
> <mailto:Albert.Whale at it-security-inc.com>> wrote:
> >>
> >> So what happens if you start Suricata in IPS Mode?
> >>
> >>
> >> On 9/24/18 2:17 PM, fatema bannatwala wrote:
> >>
> >> Hi Albert,
> >>
> >> I am running Suricata in IDS mode.
> >>
> >> Thanks,
> >> Fatema.
> >>
> >> On Mon, Sep 24, 2018 at 2:11 PM Albert E Whale
> <Albert.Whale at it-security-inc.com
> <mailto:Albert.Whale at it-security-inc.com>> wrote:
> >>>
> >>> Hi Fatema,
> >>>
> >>> I’m curious, are running Suricata in IDS or IPS mode?
> >>>
> >>> I am experiencing significant issues with IPS on a
> small home office environment.
> >>>
> >>> Sent from my iPhone
> >>>
> >>> > On Sep 24, 2018, at 1:26 PM, fatema bannatwala
> <fatema.bannatwala at gmail.com
> <mailto:fatema.bannatwala at gmail.com>> wrote:
> >>> >
> >>> > Hi All,
> >>> >
> >>> > I am working on getting Suricata up and running
> with same rulesets as we have for snort.
> >>> > Hence running Suricata with both VRT open source
> free ruleset from Cisco as well as with ET-PRO rule
> sets from Proofpoint for suricatav4.0.4.
> >>> >
> >>> > When I start Suricata it gives some errors for
> around 200 VRT rules concerning
> Invalid_Signature/Unknown_Keyword, which make sense as
> they are not designed to be run with Suricata. But
> Suricata starts up correctly and works fine inspite of
> those rule errors.
> >>> >
> >>> > My concern is, the number of unique alerts that
> get triggered in Snort are more than the unique alerts
> triggered in Suricata, even though both are getting
> same traffic flow. The difference is huge, i.e. 241
> unique Snort alerts compared to only 94 unique alerts
> in Suricata.
> >>> >
> >>> > When did an analysis, the difference is between
> ETPRO alerts as well as VRT alerts that are triggered
> in both. And confirmed that the sids that are getting
> triggered in snort are also enabled in suricata, but
> still no suricata alerts for those sids.
> >>> >
> >>> > Hence, my question is why there is this
> discrepancy in the alerts that get triggered in snort
> and not in suricata even when they both are seeing the
> same traffic and have same sids enabled?
> >>> >
> >>> > P.S My initial thought was, either it's because
> of capture loss in suricata (which is <0.1%), or maybe
> because of some of those incompatible VRT alerts that
> are enabled in Suricata, and it is not able to work
> correctly because of those.
> >>> >
> >>> > Has anyone tried this kind on config before?
> >>> >
> >>> > Thanks,
> >>> > Fatema.
> >>> >
> >>> >
> >>> > _______________________________________________
> >>> > Suricata IDS Users mailing list:
> oisf-users at openinfosecfoundation.org
> <mailto:oisf-users at openinfosecfoundation.org>
> >>> > Site: http://suricata-ids.org | Support:
> http://suricata-ids.org/support/
> >>> > List:
> https://lists.openinfosecfoundation.org/mailman/listinfo/oisf-users
> >>> >
> >>> > Conference: https://suricon.net
> >>> > Trainings: https://suricata-ids.org/training/
> >>>
> >>
> >> --
> >> --
> >>
> >> Albert E. Whale, CEH CHS CISA CISSP
> >> President - Chief Security Officer
> >> IT Security, Inc. - A Service Disabled Veteran
> Owned Company - (SDVOSB)
> >> HUBZone Certified
> >> LinkedIn Profile
> >>
> >>
> >> Phone: 412-515-3010 | Email:
> Albert.Whale at IT-Security-inc.com
> >> Cell: 412-889-6870
> >>
> > _______________________________________________
> > Suricata IDS Users mailing list:
> oisf-users at openinfosecfoundation.org
> <mailto:oisf-users at openinfosecfoundation.org>
> > Site: http://suricata-ids.org | Support:
> http://suricata-ids.org/support/
> > List:
> https://lists.openinfosecfoundation.org/mailman/listinfo/oisf-users
> >
> > Conference: https://suricon.net
> > Trainings: https://suricata-ids.org/training/
>
>
>
> --
> Michael Shirk
> Daemon Security, Inc.
> https://www.daemon-security.com
>
> _______________________________________________
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>
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>
>
>
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>
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