My ISP issues 2Wire modem/router/WAP boxes now. I found it very
interesting to explore what (few) changes require a password and what
ones do not.
In particular, packet filter and port forwarding changes require no
password at all - so changing your password on the router wouldn't do
you any good against driveby changes to those settings. I'll have to
look when I get home whether DNS server changes would.
A bit OT, but there's also the fact that since these devices are
considered ISP equipment - they include the modem that connects to
telco lines - the ISP has one, global, password for all home routers
on their network, and can admin them from the 'outside' of your home
network. Given big telco security standards, not a very reassuring
thought.
Regards
Mark
On 2/15/07, Zulfikar Ramzan wrote:
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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