Solved

block https tunnelling with squid

Posted on 2009-05-06
3
2,871 Views
Last Modified: 2012-05-06
Hi, how can I block http & https Tunneling with squid? without stopping normal traffic.
Thanks
0
Comment
Question by:Dasdan
3 Comments
 
LVL 16

Expert Comment

by:Malmensa
Comment Utility
You can't.  HTTPs is encrypted, Squid therefore cannot tell what is in each packet. If you can identify a lot of HTTPs traffic going to a particular site, you could block it by IP.  Kinda cat & mouse game with your users though.
0
 
LVL 7

Expert Comment

by:mchkorg
Comment Utility
Hi, nice subject

Some things to do :
1) when you know someone is using a https server to tunnel some traffic, you might just want to block its IP. But he'll use another one...

2) If your user is tunneling with SSH on a SSH server running on port 443 (to make squid think it's just allowed https traffic), you have to detect the so-called https server is a SSH server. Just telnet to its IP on port 443, you'll see it (except if your user has recompiled the ssh server to make it answer like a web server... or if he managed to detect it's not coming from him but from someone else and is thus redirecting traffic to a real https server - this guy would be really boring), see :
telnet my.ssh.server 443
Trying 88.x.y.z...
Connected to my.ssh.server.
Escape character is '^]'.
SSH-2.0-OpenSSH_5.1p1 Debian-5

But again, you'll just have to block the IP.

3) depending on your company, you might remind everyone the rules of your company's internet access, particularily on tunneling stuff, for security concerns. He might stop, knowing he's being watched.

4) if it's a pure stunnel, I don't think you can detect anything. You'll just have some clues about the guy and then can discuss, see point 3

5) maybe an advanced sniffing technique might give the proof it's something tunneled... but what would be the cost of detecting this for every https traffic...

Just a tip: when someones uses internet a lot and just have a few CONNECT hits in squid's log, he's tunneling everything :) that might help analyzing the logs

GOOD LUCK
0
 

Accepted Solution

by:
Dasdan earned 0 total points
Comment Utility
Hi I worked out a solution, I installed active wall from http://en.lanctrl.com/ on a dual interface pc put the interfaces in bridge mode and then setup the software to monitor one ip address from my proxy (the only ip allowed out on http/https).  In the filter section of the software it can detect https and http tunneling not sure how it does it, but it works.

A cheap solution to a sticky problem with a single ip licence only $25 and all I need to monitor is the proxy ip

Thanks for you help
0

Featured Post

What Should I Do With This Threat Intelligence?

Are you wondering if you actually need threat intelligence? The answer is yes. We explain the basics for creating useful threat intelligence.

Join & Write a Comment

Suggested Solutions

Article by: btan
Provide an easy one stop to quickly get the relevant information on common asked question on Ransomware in Expert Exchange.
Transferring data across the virtual world became simpler but protecting it is becoming a real security challenge.  How to approach cyber security  in today's business world!
It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. It works on many operating systems, in many languages.
Illustrator's Shape Builder tool will let you combine shapes visually and interactively. This video shows the Mac version, but the tool works the same way in Windows. To follow along with this video, you can draw your own shapes or download the fileā€¦

771 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

11 Experts available now in Live!

Get 1:1 Help Now