[LINK] FBI & DNSChanger Malware
stephen at melbpc.org.au
stephen at melbpc.org.au
Thu Nov 10 19:05:56 AEDT 2011
DNS (Domain Name System) is an Internet service that converts user-
friendly domain names into the numerical Internet protocol (IP) addresses
that computers use to talk to each other.
When you enter a domain name, such as www.fbi.gov, in your web browser
address bar, your computer contacts DNS servers to determine the IP
address for the website. Your computer then uses this IP address to
locate and connect to the website. DNS servers are operated by your
Internet service provider (ISP) and are included in your computers
network configuration. DNS and DNS Servers are a critical component of
your computers operating environmentwithout them, you would not be able
to access websites, send e-mail, or use any other Internet services.
Criminals have learned that if they can control a users DNS servers,
they can control what sites the user connects to on the Internet.
By controlling DNS, a criminal can get an unsuspecting user to connect to
a fraudulent website or to interfere with that users online web
browsing. One way criminals do this is by infecting computers with a
class of malicious software (malware) called DNSChanger.
In this scenario, the criminal uses the malware to change the users DNS
server settings to replace the ISPs good DNS servers with bad DNS
servers operated by the criminal. A bad DNS server operated by a criminal
is referred to as a rogue DNS server.
The FBI has uncovered a network of rogue DNS servers and has taken steps
to disable it.
The FBI is also undertaking an effort to identify and notify victims who
have been impacted by the DNSChanger malware.
One consequence of disabling the rogue DNS network is that victims who
rely on the rogue DNS network for DNS service could lose access to DNS
To address this, the FBI has worked with private sector technical experts
to develop a plan for a private-sector, non-government entity to operate
and maintain clean DNS servers for the infected victims. The FBI has also
provided information to ISPs that can be used to redirect their users
from the rogue DNS servers to the ISPs own legitimate servers.
The FBI will support the operation of the clean DNS servers for four
months, allowing time for users, businesses, and other entities to
identify and fix infected computers. At no time will the FBI have access
to any data concerning the Internet activity of the victims.
It is quite possible that computers infected with this malware may also
be infected with other malware. The establishment of these clean DNS
servers does not guarantee that the computers are safe from other
malware. The main intent is to ensure users do not lose DNS services.
What Does DNSChanger Do to My Computer?
DNSChanger malware causes a computer to use rogue DNS servers in one of
First, it changes the computers DNS server settings to replace the ISPs
good DNS servers with rogue DNS servers operated by the criminal.
Second, it attempts to access devices on the victims small office/home
office (SOHO) network that run a dynamic host configuration protocol
(DHCP) server (eg. a router or home gateway). The malware attempts to
access these devices using common default usernames and passwords and, if
successful, changes the DNS servers these devices use from the ISPs good
DNS servers to rogue DNS servers operated by the criminals. This is a
change that may impact all computers on the SOHO network, even if those
computers are not infected with the malware.
Am I Infected?
The best way to determine if your computer or SOHO router has been
affected by DNSChanger is to have them evaluated by a computer
professional. However, the following steps can help you gather
information before consulting a computer professional.
To determine if a computer is using rogue DNS servers, it is necessary to
check the DNS server settings on the computer. If the computer is
connected to a wireless access point or router, the settings on those
devices should be checked as well.
Checking the Computer:
If you are using a Windows computer, open a command prompt. This can be
done by selecting Run from the Start Menu and entering cmd.exe or
starting the command prompt application, typically located in the
Accessories folder within Programs on your Start Menu, as shown below:
At the command prompt, enter: ipconfig /all
Look for the entry that reads DNS Servers
The numbers on this line and the line(s) below it are the IP addresses
for your DNS servers. These numbers are in the format of nnn.nnn.nnn.nnn,
where nnn is a number in the range of 0 to 255. Make note of the IP
addresses for the DNS servers and compare them to the table of known
rogue DNS servers listed later in this document. If the IP addresses of
your DNS server appear in the table below, then the computer is using
You can also look for your DNS servers without using the command prompt.
For windows XP machines, click on Start and select My Network Places.
Then select Network Connections. In this example, the wireless connection
Click on the connection that is active. This will bring up the Network
Connection Status screen. Click on Support and then Details. Check for
the values that correspond to the DNS servers.
If you are using an Apple computer, click on the Apple in the top left
corner and choose System Preferences. Then, from the Apple System
Preferences window, choose Network.
The Apple Network pane will show a number of possible connections on the
left side. Choose the one that is active for you and click on the
Advanced button in the right lower corner. Then choose DNS from the
options to show the DNS servers you are using.
Compare whether your computer has DNS servers listed in the number ranges
Rogue DNS Servers
126.96.36.199 through 188.8.131.52
184.108.40.206 through 220.127.116.11
18.104.22.168 through 22.214.171.124
126.96.36.199 through 188.8.131.52
184.108.40.206 through 220.127.116.11
18.104.22.168 through 22.214.171.124
To make the comparison between the computers DNS servers and this table
easier, start by comparing the first number before the first dot. For
example, if your DNS servers do not start with 85, 67, 93, 77, 213, or
64, you can move on to the next step. If your servers start with any of
those numbers, continue the comparison.
If your computer is configured to use one or more of the rogue DNS
servers, it may be infected with DNSChanger malware.
Home computers with high-speed Internet connections and office computers
typically obtain their IP settings via DHCP from a device on the network.
In these cases, the computers are provided with an IP address, default
gateway, and DNS server settings. The IP addresses usually fall into one
of three ranges of private addresses192.168.0.0 to 192.168.255.255;
172.16.0.0 to 172.31.255.255; and 10.0.0.0 to 10.255.255.255. In most
homes, computers are assigned an IP address in the range 192.168.1.2 to
192.168.1.254, and the default gateway and DNS servers are set to
192.168.1.1. To determine if your computer is utilizing the rogue DNS
servers, read the next section, Checking the Router.
If you are unable to locate your DNS server settings, obtain assistance
from the Help program bundled with your operating system, reputable
online sources, or a trusted professional.
Checking the Router
Small office/home office routers connect your network of computers and
devices to your Internet service provider. The SOHO router may have been
purchased and installed by you or installed by your ISP. Linksys, D-Link,
Netgear, and Cisco are common SOHO router brands, but there are many
The DNSChanger malware is capable of changing the DNS server settings
within SOHO routers that have the default username and password provided
by the manufacturer. If you did not change the default password at the
time the SOHO router was installed, you must check the SOHO router
The procedure to access your SOHO router setting varies by manufacturer,
so consult your product documentation. Once you have access to the SOHO
router configuration, compare the DNS servers listed to those in the
rogue DNS servers table above. If your SOHO router is configured to use
one or more of the rogue DNS servers, a computer on your network may be
infected with DNSChanger malware.
What Should I Do?
In addition to directing your computer to utilize rogue DNS servers, the
DNSChanger malware may have prevented your computer from obtaining
operating system and anti-malware updates, both critical to protecting
your computer from online threats. This behavior increases the likelihood
of your computer being infected by additional malware. The criminals who
conspired to infect computers with this malware utilized various methods
to spread the infections. At this time, there is no single patch or fix
that can be downloaded and installed to remove this malware. Individuals
who believe their computer may be infected should consult a computer
Individuals who do not have a recent back-up of their important
documents, photos, music, and other files should complete a back-up
before attempting to clean the malware or utilize the restore procedures
that may have been packaged with your computer.
Information regarding malicious software removal can be found at the
website of the United States Computer Emergency Readiness Team:
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