<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Helvetica;
panose-1:0 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoPlainText, li.MsoPlainText, div.MsoPlainText
{mso-style-priority:99;
mso-style-link:"Plain Text Char";
margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.PlainTextChar
{mso-style-name:"Plain Text Char";
mso-style-priority:99;
mso-style-link:"Plain Text";
font-family:"Calibri",sans-serif;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style>
</head>
<body lang="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal">> The Zeek log set the auth_success state to true, but the admin of the box claims no successful login and is pushing back that it is a false positive.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">> Have other Zeek users ever seen this? Is the SSH auth state detection mistaken here?
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It’s been my experience that auth_success isn’t reliable enough to be actionable.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Melissa <o:p></o:p></p>
<p class="MsoNormal">- -<o:p></o:p></p>
<p class="MsoPlainText">Melissa Muth<o:p></o:p></p>
<p class="MsoPlainText">IT Architect, Office of Information Security<o:p></o:p></p>
<p class="MsoPlainText">Information Systems & Computing<o:p></o:p></p>
<p class="MsoPlainText">University of Pennsylvania<o:p></o:p></p>
<p class="MsoPlainText">muthm@isc.upenn.edu 215-573-6798<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black"><zeek-bounces@zeek.org> on behalf of Jim Mellander <jmellander@lbl.gov><br>
<b>Date: </b>Monday, September 16, 2019 at 3:09 PM<br>
<b>To: </b>"Collyer, Jeffrey W (jwc3f)" <jwc3f@virginia.edu><br>
<b>Cc: </b>Bro <bro@bro.org><br>
<b>Subject: </b>Re: [Zeek] SSH auth_success state true set, but admin claims no logins<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Since Zeek only sees the encrypted traffic of an ssh session, it can only make a best-guess based on packet-size analysis, which is not necessarily going to be 100% accurate.<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On Mon, Sep 16, 2019 at 11:24 AM Collyer, Jeffrey W (jwc3f) <<a href="mailto:jwc3f@virginia.edu">jwc3f@virginia.edu</a>> wrote:<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">So recently I saw an SSH login to a device from outside the US. I reported it to the end system admin. The Zeek log set the auth_success state to true, but the admin of the box claims no successful login and is pushing back that it is
a false positive. <o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Have other Zeek users ever seen this? Is the SSH auth state detection mistaken here?
<o:p></o:p></p>
<div>
<p class="MsoNormal">I don’t have pcaps to verify one way to the other, sadly.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">{"_path":"ssh","_system_name":"corelight","_write_ts":"2019-09-12T22:26:32.106142Z","ts":"2019-09-12T22:26:31.226136Z","uid":"C95i0o2Jl77LXHb2R9","id.orig_h”:”x.x.x.x","id.orig_p":49670,"id.resp_h”:”x.x.x.x","id.resp_p":22,"version":2,"auth_success":true,"auth_attempts":1,"direction":"INBOUND","client":"SSH-2.0-OpenSSH_7.2p2
Ubuntu-4ubuntu2.4","server":"SSH-2.0-OpenSSH_7.4","cipher_alg":"<a href="mailto:chacha20-poly1305@openssh.com" target="_blank">chacha20-poly1305@openssh.com</a>","mac_alg":"<a href="mailto:umac-64-etm@openssh.com" target="_blank">umac-64-etm@openssh.com</a>","compression_alg":"none","kex_alg":"<a href="mailto:curve25519-sha256@libssh.org" target="_blank">curve25519-sha256@libssh.org</a>","host_key_alg":"ecdsa-sha2-nistp256","host_key":"68:1e:68:89:5e:e5:20:72:f7:e6:bf:21:de:07:3a:b1”}<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Can anyone shed light on this?<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Thanks<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Jeff<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal"><span style="font-size:13.5pt;font-family:Helvetica;color:black">Jeffrey Collyer<br>
Information Security Engineer<br>
University of Virginia<br>
<a href="mailto:jwc3f@virginia.edu" target="_blank">jwc3f@virginia.edu</a><o:p></o:p></span></p>
</div>
</div>
</div>
</div>
</div>
<p class="MsoNormal">_______________________________________________<br>
Zeek mailing list<br>
<a href="mailto:zeek@zeek.org" target="_blank">zeek@zeek.org</a><br>
<a href="http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/zeek" target="_blank">http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/zeek</a><o:p></o:p></p>
</div>
</body>
</html>