Brian Krebs at his Security Fix column at the Washington Post reported last week:

Malware Silently Alters Wireless Router Settings

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. DNS can be thought of as the Internet’s phone book, translating human-friendly names like example.com into numeric addresses that are easier for networking equipment to handle.

Much more in the article!

We have always recommended changing your router’s default settings like username/password combination, as well as the standard wireless SSID and channel and applying the latest firmware patches for your router.

Also turn off UPNP (Universal Plug’N’Play) in the router. And use WPA security whenever possible for your wireless users to protect your network and keep nefarious users from spreading spam or other bad things through your wireless Internet connection.

And as one of the comments noted:

Besides a non-admin (limited user)* account and AV software, another effective defense against these types of malware is a blocking hosts file:

http://www.mvps.org/winhelp2002/hosts.htm

They also have a related blog that covers a lot of these types of malware tricks using codecs.

http://msmvps.com/blogs/hostsnews/default.aspx

Thanks striker in this topic at Scot’s Newsletter Forums for the heads up on this one.

* Where possible (generally easier on Linux, Mac and Vista to run as a limited user than previous versions of Windows like WinXP, and earlier).

Unfortunately even printing can be a challenge in some versions of Windows (WinXP) depending upon the type of printer, if you are using a limited account.

However, if and when you can, either running as a limited user, or using a Linux LiveCD (LiveCD List) to surf the web would be a much safer way to surf the web in general, as well as making sure your router’s information has been updated as noted above regardless.

NOTE: If you adjust your settings on that LiveCD page, you can even find Linux LiveCDs for PPC Macs. I have tried and really like the Ubuntu LiveCD for the PPC Mac.

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