<html xmlns:v="urn:schemas-microsoft-com:vml" 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=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@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;}
span.EmailStyle17
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.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><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>What is the experience out there with allowing public telnet access to JNOS? And, if you do allow it on your machine, what security measures have you taken?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Some background: <o:p></o:p></p><p class=MsoNormal>On my Linux machine, I have iptables rules to avoid SYN attacks and rules to avoid more than X number of connections from a given host within Y amount of time. These apply to connections to linux as well as connections forwarded across the tunnel to JNOS. This puts a damper on brute force attacks such as dictionary attacks. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>However, linux is also running DenyHosts which is set to disallow (forever) connections from machines that have more than X failed login attempts in a row. This pretty much kills dictionary attacks except if they come from multiple machines. Every day, I record at least one (sometimes two or three) machines that have been added to the denyhosts file. So I know for sure that there is a constant flow of attack.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Since something like DenyHosts is not available at the JNOS level, the iptables rules can slow down, but not completely stop brute force attacks from a given hosts. So, I’m wondering if anyone with public telnet access has any other tricks up their sleeve for helping to secure JNOS.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks,<o:p></o:p></p><p class=MsoNormal>Michael<o:p></o:p></p><p class=MsoNormal>N6MEF<o:p></o:p></p></div></body></html>