There are several built-in Top-K algorithms (volume, upload, download, duration, based on ports, IPs, subnets, netflow). Flow Tracking is a streaming algorithm which plugs into the flows stream and continously snapshots Top-K every minute. We create a SSH Flow Tracker to first get baseline visibility and then to incrementally refine the tracking until we get a workable list of suspect flows. Here are some techniques we use in Trisul, you should be able to adapt these to your own toolchain. Therefore any naive SSH flow monitoring is going to be dominated by legitimate business applications. In any large organization SSH is going to be pervasive. It is quite obvious that any monitoring platform needs to help organizations stay right on top of SSH. Autossh is a very advanced tool that maintains the tunnel and keeps it from timing out. 24×7 access into your network : reverse ssh tunnels can give outsiders persistent presence into deep parts of your inside network.This pretty much defeats every policy control you have at the boundary. dynamic forwarding used as proxy using dynamic port forwarding users can proxy web traffic through the encrypted tunnel.
single flow : when you are monitoring on the perimeter SSH tunnels show up as a single flow while they multiplex several SSH or SFTP channels.Here are the top three ways in which SSH tunnels create blind spots for NSM tools Reverse SSH tunnel allows someone to log on to an outside machine and pop up on the inside! 3 ways in which SSH tunnels create blind spots for monitoring
#Reverse ssh tunnel manager full
SSHv2 -D allows a full SOCK5 proxy outside your visibility zone Here is how a Forward SSH tunnel looks like F orward SSH tunnel hides activity.
The reverse tunnel is also called an autossh tunnel after the popular tool used to setup and maintain this connection. The reverse tunnel allows an outsider to get on the inside. The forward tunnel allows an insider to get on the outside bypassing the NSM and Firewall/NAT sentries. With HTTPS/SSL, security tools can get atleast a look at the unencrypted certificates and perform checks, with SSH everything goes dark right after the initial capabilities exchange. SSHv2 even has SOCKS5 support – this allows anyone to setup a full SOCKS5 proxy outside your network and hide all HTTP activity from the prying eyes of NSM tools. Many users also use the less well known port forwarding feature of SSH to create ‘tunnels’. SSH tunnels bore through firewalls, NATs, and are almost totally opaque to Network Security Monitoring tools like Trisul, Bro, Suricata, Snort, and others. The most common use of SSH is for totally legitimate purposes like terminal ( ssh) or for file transfer ( scp, sftp). SSH is an incredibly powerful protocol whose footprint needs to be monitored closely in enterprises.
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