nanog mailing list archives

RE: Security problem in PPPoE connection


From: "Bora Akyol" <bora () broadcom com>
Date: Mon, 13 Mar 2006 11:16:25 -0800


Any info on percentages of users that use routers vs Windows boxes? 



Microsoft has some suggestions for configuring PPPOE for MS-Windows.

http://www.microsoft.com/technet/prodtechnol/winxppro/maintain
/pppoe.mspx

A problem is many of your customers won't follow the 
directions, and may still be vulnerable to man-in-the-middle 
attacks for the login if they don't disable PAP. Because 
things will appear to work, i.e. Windows will use CHAP first 
and fallback to PAP, your customers may not notice when an 
attack does occur.

Although PPPOE is a layer 2 protocol, the user data may be 
vulnerable to many of the same ethernet CAM table, denial of 
service and sniffing weaknesses even if the login credentials 
are kept secret with CHAP (or more advanced EAP options).  
PPPOE and PPP tend to assume the access networks are 1) 
"free" and 2) "secure."  This may be constrained using 
point-to-point connections, but often require additional 
configuration of multi-access networks.

The configuration details will vary by equipment vendor.  But 
you should find some good information by doing a few web 
searches for metro ethernet security, private vlan, broadcast 
security.




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