Firewall Wizards mailing list archives
RE: Prohibiting SSL VPNs
From: "Melson, Paul" <PMelson () sequoianet com>
Date: Fri, 21 May 2004 15:04:04 -0400
-----Original Message----- Does anybody have any ideas on how I could prohibit the usage of SSL VPNs like the one offered by F5 (Firepass), since this requires only the ability for the client to make an https connection (bypassing any kind of firewall/proxy)? Since this product (or any similar) creates some kind of PPP connection over https, installs routes on the PC etc. it will create a lot of problems. (see also: Worms, Air Gaps etc)
access-list 101 deny tcp any any eq 443 :-)
I know that I could possibly stop the downloading of ActiveX/Java applets via some kind of web filtering software but this also has a lot of side effects, or I could use some kind of whitelist for https connections, but this is too difficult to manage/maintain.
Before you can intercept Java applets you'll need to terminate the SSL stream at some inspection point that you control. Easier said than done. Most proxies that "support" HTTPS/SSL just allow HTTP CONNECT sessions through the proxy for traffic destined for TCP/443. Also consider that if they are resourceful, your users can use SSL tunneling over nearly any port you allow out through your firewall that doesn't have some sort of application proxy to facilitate (and normalize) traffic. Realistically, your best bet is to set an organizational policy that forbids the use of such services/connections and to communicate that to users. This is similar to the GoToMyPC.com issue. You can block access to some IP addresses and hope they don't change or that your users don't find another service you don't know about. Or you can block all access to encrypted protocols, which is a big pain and may create other business problems, and probably still won't keep that 0.01% of your users from misbehaving. PaulM _______________________________________________ firewall-wizards mailing list firewall-wizards () honor icsalabs com http://honor.icsalabs.com/mailman/listinfo/firewall-wizards
Current thread:
- Prohibiting SSL VPNs John Kougoulos (May 21)
- Re: Prohibiting SSL VPNs Frederick M Avolio (May 21)
- Re: Prohibiting SSL VPNs John Kougoulos (May 25)
- Re: Prohibiting SSL VPNs Paul D. Robertson (May 21)
- <Possible follow-ups>
- RE: Prohibiting SSL VPNs Melson, Paul (May 21)
- RE: Prohibiting SSL VPNs Desai, Ashish (May 21)
- Re: Prohibiting SSL VPNs Frederick M Avolio (May 21)