Category Archives: SSL VPN

Advanced Persistent Surveillance: SSH Connectivity

Today I read about a Juniper announcement that unauthorized code in Juniper firewalls can allow an attacker to listen in on conversations, even decrypting communications by using your firewall as a MITM. A second, unrelated according to the company, announcement concerned a pair of exploits, one that allows an attacker telnet or ssh access into the device and that a “knowledgeable” user could also decrypt vpn traffic once the firewall had been compromised. While they say that there is no way to tell if you have been victim of this exploit, there are some ways you can check to see if there is any malicious activity on your devices and you CAN do so without sifting through a terabyte of log files.

Most Juniper customers will shut telnet off in favor of ssh so I will focus on how to use wire data analytics to monitor for potential malicious behavior over ssh.

First, I am not what you would call an INFOSEC expert. I worked in IT Security for a few years handling event correlation and some perimeter stuff but I firmly believe that anyone that is responsible for ANYTHING with an IP address should consider themselves a security practitioner, at least for those systems under their purview. I would consider myself more of a “packet jockey”. I am a Solutions Architect for a Wire Data analytics company, ExtraHop Networks. I have spent the better part of the last two years sitting at the core of several large enterprises looking at packets and studying behavior. Today I will go over why it is important to monitor any and all ssh connections and I will discuss why logs aren’t enough.

Monitoring SSH:
While the article states “There is no way to detect that this vulnerability was exploited.”, I would say that if you see a non RFC1918 address SSH-ing into your firewall, something needs to be explained. Currently, most teams monitor ssh access by syslogging all access attempts to a remote syslog server where they can be observed, hopefully, in time to notify someone that there has been unauthorized activity. The issue here is that once someone compromises the system, if they are worth their weight in salt, the first thing they do is turn off logging. In addition, the act of sifting through syslogs can be daunting and time consuming and at times does not deliver the type of agility needed to respond to an imminent threat.

Enter ExtraHop Wire Data Analytics:

What I like about wire data analytics is that you are not dependent on a system to self-report that it has been compromised. Simply put you cannot hide from ExtraHop, we will find you! Yes, you can breach the Juniper firewall (or any other ssh enabled device) and shut logging off but you cannot prevent us from seeing what you are doing.

*(I am assuming you can shut logging off, I know you can on the ASA’s but I have never administered a Juniper firewall so don’t quote me on that but most devices have to be told what and where to log).

On the wire, there is nowhere to hide, if you are coming from an IP address and you are connecting to another IP address, you’re busted. Whether you are running a “select * from …” on the production database server, SCPing the company leads to your home FTP server or compromising a firewall. ExtraHoop offers several ways to monitor ingress and egress traffic, today I am going to discuss how we can monitor ssh via the Discover Appliance as well as how to leverage our new big data platform, our Explorer Appliance.

Using the Discover Appliance to monitor SSH Traffic:

One of the first and easiest ways to check and see if you have had anyone ssh into your firewall is to simply browse to it in the UI and go to L7 protocols and look for SSH.

Click to enlarge


Click to enlarge

You can also build a quick dashboard showing who has ssh’d into the box and make it available for your SOC to view and alert you on. The dashboard below is showing the number of inbound SSH packets. You see the source IP of as well as 23 inbound packets. We can also show you outbound packets as well.

This can all be done literally within 5 minutes and you can have total visibility into any ssh session that connects to your Juniper firewall, or ANY ssh enabled device, or ANY device over ANY port or protocol.

Can we have an alert? Yes, ExtraHop has a full alerting system that allows you to alert on any ssh connection to your gateway devices.

Monitoring SSH via the ExtraHop Explorer Appliance:

A few weeks ago, ExtraHop introduced their Explorer Appliance. This is an accompanying appliance that allows you to write flows and layer 7 metrics to a big data back end as part of a searchable index. In the example I am going to show you I will be speaking specifically about “Flow” records. ExtraHop can surgically monitor any port for any device and write them out to the explorer appliance. For Flow records, since they are very intense, we do not automatically log them, we recommend that you set them on a per host basis from the Admin console. Once added, any and all communications will be audited and searchable for that host.

To audit ssh connectivity of our Juniper Firewall we will go to the discovered device and select the parent node. From there on the right hand side you will see an “ExtraHop ID:” (Note the Search Textbox above it)

Click to enlarge


You will past the device ID into the search box and click “Global Records Query”

Click to enlarge

This will be the initial default filter, you will then add a 2nd Filter as seen below by setting the receiver port to 22

Click to enlarge

Now that you have the ExtraHop Device ID and Port 22 set as a filter, you can see below that you are able to audit, both in real-time and in the past, any/all ssh sessions to your Juniper firewall or any other device that you wish to monitor on any other port. You can save this query and come back to it periodically as a method of ongoing auditing of your firewall and ssh traffic.

Click to enlarge

What am I looking for here?
For me, I would be interested in any non-RFC1918 addresses, the number of bytes and the source host. If you notice that it is a laptop from the guest wireless network (or the NATed IP of the Access Point) then that may be something to be concerned with. As I stated earlier, while the announcement stated that you cannot tell if the exploit has been used, I think consistent auditing using wire data gives them no place to hide if they do compromise your ssh-enabled appliance and it is generally a good idea to monitor ssh access. In the real-time grid above, you can see the sender “” is ssh’d into our Juniper Firewall. Does not matter if the first thing they do is shut of logging or if it is an insider who controls it. They can’t hide on the wire.

ExtraHop offers a full alerting suite that can whitelist specific jump boxes and hosts and provide visibility into just those hosts who you do not expect to see ssh’d into any system you have as well as the ability to monitor any other ingress or egress traffic that may look out of the ordinary. (Example: A SQL Server FTPing to a site in China or someone accessing a hidden share that is not IPC$).

At the end of the day, the next big breach will involve one host talking to another host that they were not supposed to, weather that is my credit card number being SCP’d to Belarus or my SF86 form being downloaded by China. Advanced Persistent Surveillance of critical systems is the best way to prepare yourself and your system owners for tomorrow’s breach. While I am very thankful to the INFOSEC community for all that they do, for a lot of us, by the time a CVE is published, it is too late. The next generation of digital vigilance will involve hand-to-hand combat and no one will give you a sharper knife or a bigger stick than Wire Data Analytics with ExtraHop.

Thank you for Reading!