New Zlob Trojan Alters Your Router Settings

June 12, 2008 – 5:59 AM

Another new development in the malware arena, this new version of Zlob will actually log onto your router and change the DNS settings to hijack your traffic.

Pretty interesting approach and it will work because 99% of people won’t change the default password on their routers. Let’s face it, have you changed it?

A new Trojan horse masquerading as a video “codec” required to view content on certain Web sites tries to change key settings on the victim’s Internet router so that all of the victim’s Web traffic is routed through servers controlled by the attackers.

According to researchers contacted by Security Fix, recent versions of the ubiquitous “Zlob” Trojan (also known as DNSChanger) will check to see if the victim uses a wireless or wired hardware router. If so, it tries to guess the password needed to administer the router by consulting a built-in list of default router username/password combinations. If successful, the malware alters the victim’s domain name system (DNS) records so that all future traffic passes through the attacker’s network first.

It’s a pretty nifty piece of logic and coding, pretty simple too once you’ve thought of the idea. Just grep the gateway address from the machine (using the correct interface) then try and connect to it with a pre-compiled list of default user names and passwords.

Then bingo you’re in a little insertion of new DNS servers and you’re set!

Relatively few people ever change the default username and password on their wireless routers. I see this often, even among people who have locked down their wireless routers with encryption and all kinds of other security settings: When I confront them about why they haven’t changed the default credentials used to administer the router settings, their rationale is that, ‘Well, why should I change it? An attacker would need to already have a valid connection on my network in order to reach the router administration page, so what’s the difference?’

Obviously, an attack like this illustrates the folly of that reasoning.

Indeed flawed reasoning, you should never leave anything with default passwords if possible as it’s just another weakness waiting to be exploited.

Not to say you will get infected with this malware, because that is unlikely, but someone on your network might…and if you haven’t changed the password the hijack could effect you too (it wouldn’t effect me because my DNS servers are static in my network interface settings as set by me).

Source: Darknet