SecurityFocus HOME Infocus: Penetration Testing IPsec VPNs: "Penetration Testing IPsec VPNs
by Rohyt Belani and K.K. Mookhey
last updated February 9, 2005
1. Introduction
As companies expand their presence globally, there arises a need for secure electronic communications between geographically dispersed locations. Virtual private networks (VPNs) provide an economically viable option to address this need."
All IT managers need to understand the points made in this article. The VPN can be the single most exposed point on the corporate network. Given a list of usernames, cracking the VPN is a great way to get ownership of the whole corporate LAN since most are configured for unfettered access to all devices in the LAN. And if there is a site to site VPN in aggressive mode with PreSharedKeys (PSK), then it is trivial to force the VPN server to send the PSK HASH, from which you can easily bruteforce the PSK at leisure on your own system. This can all be done without triggering any major alerts or doing noisy/detectable scans. -Bryan
