<s>
DNSChanger	B-Application
is	O
a	O
DNS	B-Protocol
hijacking	I-Protocol
Trojan	O
.	O
</s>
<s>
The	O
work	O
of	O
an	O
Estonian	O
company	O
known	O
as	O
Rove	O
Digital	O
,	O
the	O
malware-infected	O
computers	O
by	O
modifying	O
a	O
computer	O
's	O
DNS	B-Protocol
entries	O
to	O
point	O
toward	O
its	O
own	O
rogue	O
name	B-Protocol
servers	I-Protocol
,	O
which	O
then	O
injected	O
its	O
own	O
advertising	O
into	O
Web	O
pages	O
.	O
</s>
<s>
At	O
its	O
peak	O
,	O
DNSChanger	B-Application
was	O
estimated	O
to	O
have	O
infected	O
over	O
four	O
million	O
computers	O
,	O
bringing	O
in	O
at	O
least	O
US$14	O
million	O
in	O
profits	O
to	O
its	O
operator	O
from	O
fraudulent	O
advertising	O
revenue	O
.	O
</s>
<s>
Both	O
Windows	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
variants	O
of	O
DNSChanger	B-Application
were	O
circulated	O
,	O
the	O
latter	O
taking	O
the	O
form	O
of	O
a	O
related	O
Trojan	O
known	O
as	O
RSPlug	B-Application
.	O
</s>
<s>
DNSChanger	B-Application
was	O
distributed	O
as	O
a	O
drive-by	O
download	O
claiming	O
to	O
be	O
a	O
video	B-Application
codec	I-Application
needed	O
to	O
view	O
content	O
on	O
a	O
Web	O
site	O
,	O
particularly	O
appearing	O
on	O
rogue	O
pornography	O
sites	O
.	O
</s>
<s>
Once	O
installed	O
,	O
the	O
malware	O
then	O
modified	O
the	O
system	O
's	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
configuration	O
,	O
pointing	O
them	O
to	O
rogue	O
name	B-Protocol
servers	I-Protocol
operated	O
through	O
affiliates	O
of	O
Rove	O
Digital	O
.	O
</s>
<s>
These	O
rogue	O
name	B-Protocol
servers	I-Protocol
primarily	O
substituted	O
advertising	O
on	O
Web	O
pages	O
with	O
advertising	O
sold	O
by	O
Rove	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
rogue	B-Protocol
DNS	I-Protocol
server	I-Protocol
redirected	O
links	O
to	O
certain	O
Web	O
sites	O
to	O
those	O
of	O
advertisers	O
,	O
such	O
as	O
,	O
for	O
example	O
,	O
redirecting	O
the	O
IRS	O
Web	O
site	O
to	O
that	O
of	O
a	O
tax	O
preparation	O
company	O
.	O
</s>
<s>
The	O
effects	O
of	O
DNSChanger	B-Application
could	O
also	O
spread	O
itself	O
to	O
other	O
computers	O
within	O
a	O
LAN	B-General_Concept
by	O
mimicking	O
a	O
DHCP	B-Protocol
server	I-Protocol
,	O
pointing	O
other	O
computers	O
toward	O
the	O
rogue	B-Protocol
DNS	I-Protocol
servers	I-Protocol
.	O
</s>
<s>
In	O
its	O
indictment	O
against	O
Rove	O
,	O
the	O
United	O
States	O
Department	O
of	O
Justice	O
also	O
reported	O
that	O
the	O
rogue	O
servers	O
had	O
blocked	O
access	O
to	O
update	O
servers	O
for	O
antivirus	B-Application
software	I-Application
.	O
</s>
<s>
On	O
October	O
1	O
,	O
2011	O
,	O
as	O
part	O
of	O
Operation	O
Ghost	O
Click	O
(	O
a	O
collaborative	O
investigation	O
into	O
the	O
operation	O
)	O
,	O
the	O
United	O
States	O
Attorney	O
for	O
the	O
Southern	O
District	O
of	O
New	O
York	O
announced	O
charges	O
against	O
six	O
Estonian	O
nationals	O
and	O
one	O
Russian	O
national	O
connected	O
to	O
DNSChanger	B-Application
and	O
Rove	O
Digital	O
for	O
wire	O
fraud	O
,	O
computer	O
intrusion	O
,	O
and	O
conspiracy	O
.	O
</s>
<s>
Due	O
to	O
concerns	O
by	O
FBI	O
agents	O
that	O
users	O
still	O
infected	O
by	O
DNSChanger	B-Application
could	O
lose	O
Internet	O
access	O
if	O
the	O
rogue	B-Protocol
DNS	I-Protocol
servers	I-Protocol
were	O
shut	O
down	O
entirely	O
,	O
a	O
temporary	O
court	O
order	O
was	O
obtained	O
to	O
allow	O
the	O
Internet	O
Systems	O
Consortium	O
to	O
operate	O
replacement	O
servers	O
,	O
which	O
would	O
serve	O
DNS	B-Protocol
requests	O
from	O
those	O
who	O
had	O
not	O
yet	O
removed	O
the	O
infection	O
,	O
and	O
to	O
collect	O
information	O
on	O
those	O
still	O
infected	O
in	O
order	O
to	O
promptly	O
notify	O
them	O
about	O
the	O
presence	O
of	O
the	O
malware	O
.	O
</s>
<s>
F-Secure	O
estimated	O
on	O
July	O
4	O
,	O
2012	O
that	O
at	O
least	O
300,000	O
computers	O
were	O
still	O
infected	O
with	O
the	O
DNSChanger	B-Application
malware	O
,	O
70,000	O
of	O
which	O
were	O
located	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
The	O
interim	O
DNS	B-Protocol
servers	I-Protocol
were	O
officially	O
shut	O
down	O
by	O
the	O
FBI	O
on	O
July	O
9	O
,	O
2012	O
.	O
</s>
<s>
Impact	O
from	O
the	O
shutdown	O
was	O
considered	O
to	O
be	O
minimal	O
,	O
due	O
in	O
part	O
to	O
major	O
Internet	O
service	O
providers	O
providing	O
temporary	O
DNS	B-Protocol
services	O
of	O
their	O
own	O
and	O
support	O
to	O
customers	O
affected	O
by	O
DNSChanger	B-Application
.	O
</s>
<s>
These	O
included	O
online	O
tools	O
that	O
could	O
check	O
for	O
the	O
presence	O
of	O
DNSChanger	B-Application
,	O
while	O
Google	B-Application
and	O
Facebook	B-Application
provided	O
notifications	O
to	O
visitors	O
of	O
their	O
respective	O
services	O
who	O
were	O
still	O
affected	O
by	O
the	O
malware	O
.	O
</s>
<s>
By	O
July	O
9	O
,	O
2012	O
,	O
F-Secure	O
estimated	O
that	O
the	O
number	O
of	O
remaining	O
DNSChanger	B-Application
infections	O
in	O
the	O
U.S.	O
had	O
dropped	O
from	O
70,000	O
to	O
42,000	O
.	O
</s>
