We discovered a new potential threat that we term "Drive-by Pharming". An
attacker can create a web page containing a simple piece of malicious
JavaScript code. When the page is viewed, the code makes a login attempt into
the user's home broadband router and attempts to change its DNS server settings
(e.g., to point the user to an attacker-controlled DNS server). Once the
user's machine receives the updated DNS settings from the router (e.g., after
the machine is rebooted) future DNS request are made to and resolved by the
attacker's DNS server.
The main condition for the attack to be successful is that the attacker can
guess the router password (which can be very easy to do since these home
routers come with a default password that is uniform, well known, and often
never changed). Note that the attack does not require the user to download any
malicious software - simply viewing a web page with the malicious JavaScript
code is enough.
We've written proof of concept code that can successfully carry out the steps
of the attack on Linksys, D-Link, and NETGEAR home routers. If users change
their home broadband router passwords to something difficult for an attacker to
guess, they are safe from this threat.
Additional details on the attack can be found at:
http://www.symantec.com/enterprise/security_response/weblog/2007/02/driveby_pharming_how_clicking_1.html
Thanks,
Zulfikar Ramzan
________________________________________
Zulfikar Ramzan
Sr. Principal Security Researcher
Advanced Threat Research
Symantec Corporation
www.symantec.com
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