At the recent DEFCON hacking conference, security researchers demonstrated a method to crack the MS-CHAPv2 authentication protocol with a 100% success rate. MS-CHAPv2 is used as the default authentication method for remote access VPN in Forefront TMG 2010.
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With the public availability of tools to automate the cracking process, PPTP communication using MS-CHAPv2 should be considered unencrypted. There are two options available to mitigate this concern: disable MS-CHAPv2 and enable EAP with PPTP, or disable PPTP and switch to a more secure remote access VPN protocol such as L2TP/IPsec or SSTP. Enabling EAP requires the use of smart cards or certificates for authentication which makes implementation more challenging. SSTP is an excellent option as it leverages SSL/TLS to protect the MS-CHAPv2 authentication process. However, SSTP is only supported on Windows Vista SP1 and later clients. L2TP/IPsec is another good choice, and although it does support certificates it can also be configured using a pre-shared key. If long, complex passwords are used and care is taken to ensure that the password is well protected, it can provide a secure remote access solution.
Good post pointing out the potential risk in PPTP VPNs, but the fact that MS-CHAPv2 has been cracked is a scary one.There are so many things dependent on this technology like wireless authentication, dailin connectivity, 802.1x implementations etc. etc. 2ff7e9595c
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