OpenVPN cannot run as a monolithic executable. It requires installation of a
software NIC. This means it can't run from removable media such as CD-ROM or
USB drive. Are we talking about Windows machines? If you block driver
installation that will keep it off your machines. The software NIC driver is
unsigned. If you need driver installation you can set policy to reject unsigned
drivers.
I don't know how you'd block OpenVPN by watching the traffic. OpenVPN defaults
to listening on UDP 1194 on the server side. But of course that can be changed.
A strict egress filtering policy may catch it...
Brent Gardner
-----Original Message-----
From: Andrew Stewart [mailto:astewart@Gestampna.com]
Sent: Thursday, March 23, 2006 2:34 PM
To: security-basics@securityfocus.com
Subject: Blocking ssl vpn connections
How would one go about blocking an SSL VPN (e.g. openVPN) on
a firewall (or even detecting it via an IDS)? I was
wondering what a network/security administrator should do to
prevent an employee from connecting to a SSL VPN from
internal to the administrator's network to some unknown SSL
VPN server. I could see this being used for numerous things
that are not in agreement with most companies acceptable use policies.
---------------------------
Andrew Stewart
Gestamp Alabama, Inc.
IT Support Tech
astewart@gestampna.com
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