<s>
A	O
DNS	B-Application
leak	I-Application
refers	O
to	O
a	O
security	O
flaw	O
that	O
allows	O
DNS	B-Application
requests	O
to	O
be	O
revealed	O
to	O
ISP	O
DNS	B-Application
servers	O
,	O
despite	O
the	O
use	O
of	O
a	O
VPN	B-Application
service	O
to	O
attempt	O
to	O
conceal	O
them	O
.	O
</s>
<s>
Although	O
primarily	O
of	O
concern	O
to	O
VPN	B-Application
users	O
,	O
it	O
is	O
also	O
possible	O
to	O
prevent	O
it	O
for	O
proxy	B-Application
and	O
direct	O
internet	O
users	O
.	O
</s>
<s>
This	O
is	O
possible	O
because	O
the	O
browser	B-Application
's	O
DNS	B-Application
requests	O
are	O
sent	O
to	O
the	O
ISP	O
DNS	B-Application
server	O
directly	O
,	O
and	O
not	O
sent	O
through	O
the	O
VPN	B-Application
.	O
</s>
<s>
This	O
only	O
occurs	O
with	O
certain	O
types	O
of	O
VPNs	B-Application
,	O
e.g.	O
</s>
<s>
"	O
split-tunnel	O
"	O
VPNs	B-Application
,	O
where	O
traffic	O
can	O
still	O
be	O
sent	O
over	O
the	O
local	O
network	O
interface	O
even	O
when	O
the	O
VPN	B-Application
is	O
active	O
.	O
</s>
<s>
Starting	O
with	O
Windows	B-Application
8	I-Application
,	O
Microsoft	O
has	O
introduced	O
the	O
"	O
Smart	O
Multi-Homed	O
Named	O
Resolution	O
"	O
.	O
</s>
<s>
This	O
altered	O
the	O
way	O
Windows	B-Application
8	I-Application
handled	O
DNS	B-Application
requests	O
,	O
by	O
ensuring	O
that	O
a	O
DNS	B-Application
request	O
could	O
travel	O
across	O
all	O
available	O
network	O
interfaces	O
on	O
the	O
computer	O
.	O
</s>
<s>
While	O
there	O
is	O
general	O
consensus	O
that	O
this	O
new	O
method	O
of	O
domain	O
name	O
resolution	O
accelerated	O
the	O
time	O
required	O
for	O
a	O
DNS	B-Application
look-up	O
to	O
be	O
completed	O
,	O
it	O
also	O
exposed	O
VPN	B-Application
users	O
to	O
DNS	B-Application
leaks	I-Application
when	O
connected	O
to	O
a	O
VPN	B-Application
endpoint	O
,	O
because	O
the	O
computer	O
would	O
no	O
longer	O
use	O
only	O
the	O
DNS	B-Application
servers	O
assigned	O
by	O
the	O
VPN	B-Application
service	O
.	O
</s>
<s>
Instead	O
the	O
DNS	B-Application
request	O
would	O
be	O
sent	O
through	O
all	O
available	O
interfaces	O
,	O
thus	O
the	O
DNS	B-Application
traffic	O
would	O
travel	O
out	O
of	O
the	O
VPN	B-Application
tunnel	O
and	O
expose	O
the	O
user	O
's	O
default	O
DNS	B-Application
servers	O
.	O
</s>
<s>
Websites	O
exist	O
to	O
allow	O
testing	O
to	O
determine	O
whether	O
a	O
DNS	B-Application
leak	I-Application
is	O
occurring	O
.	O
</s>
<s>
DNS	B-Application
leaks	I-Application
can	O
be	O
addressed	O
in	O
a	O
number	O
of	O
ways	O
:	O
</s>
<s>
Encrypting	O
DNS	B-Application
requests	O
with	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
or	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
,	O
which	O
prevents	O
the	O
requests	O
from	O
being	O
seen	O
by	O
on-path	O
eavesdroppers	O
.	O
</s>
<s>
Using	O
a	O
VPN	B-Application
client	I-Application
which	O
sends	O
DNS	B-Application
requests	O
over	O
the	O
VPN	B-Application
.	O
</s>
<s>
Not	O
all	O
VPN	B-Application
apps	O
will	O
successfully	O
plug	O
DNS	B-Application
leaks	I-Application
,	O
as	O
it	O
was	O
found	O
in	O
a	O
study	O
by	O
the	O
Commonwealth	O
Scientific	O
and	O
Industrial	O
Research	O
Organisation	O
in	O
2016	O
when	O
they	O
carried	O
an	O
in-depth	O
research	O
called	O
"	O
An	O
Analysis	O
of	O
the	O
Privacy	O
and	O
Security	O
Risks	O
of	O
Android	O
VPN	B-Application
Permission-enabled	O
Apps	O
"	O
and	O
found	O
that	O
84%	O
of	O
the	O
283	O
VPN	B-Application
applications	O
on	O
Google	B-Application
Play	I-Application
Store	I-Application
that	O
they	O
tested	O
did	O
leak	O
DNS	B-Application
requests	O
.	O
</s>
<s>
Changing	O
DNS	B-Application
servers	O
on	O
local	O
computer	O
for	O
whole	O
network	O
adapters	O
,	O
or	O
setting	O
them	O
to	O
different	O
ones	O
.	O
</s>
<s>
Using	O
a	O
firewall	B-Application
to	O
disable	O
DNS	B-Application
on	O
whole	O
device	O
(	O
usually	O
outgoing	O
connections	O
UDP	O
and	O
less	O
commonly	O
TCP	O
port	O
53	O
)	O
,	O
or	O
setting	O
dns	B-Application
servers	O
to	O
non-existing	O
ones	O
like	O
local	O
127.0.0.1	O
or	O
0.0.0.0	O
(	O
via	O
command	O
line	O
or	O
3rd	O
party	O
app	O
if	O
not	O
possible	O
via	O
OS	O
GUI	O
interface	O
)	O
.	O
</s>
<s>
This	O
requires	O
alternate	O
ways	O
of	O
resolving	O
domains	O
like	O
the	O
above	O
mentioned	O
ones	O
,	O
or	O
using	O
in	O
apps	O
with	O
configured	O
proxy	B-Application
,	O
or	O
using	O
proxy	B-Application
helper	O
apps	O
like	O
Proxifier	O
or	O
ProxyCap	O
,	O
which	O
allows	O
resolving	O
domains	O
over	O
proxy	B-Application
.	O
</s>
<s>
Many	O
apps	O
allow	O
setting	O
manual	O
proxy	B-Application
or	O
using	O
proxy	B-Application
already	O
used	O
by	O
system	O
.	O
</s>
<s>
Using	O
completely	O
anonymous	O
web	B-Application
browsers	I-Application
such	O
as	O
Tor	B-Operating_System
Browser	I-Operating_System
which	O
not	O
only	O
makes	O
user	O
anonymous	O
,	O
but	O
also	O
does	O
n't	O
require	O
any	O
dns	B-Application
to	O
be	O
set	O
up	O
on	O
the	O
operating	O
system	O
.	O
</s>
<s>
Using	O
proxy	B-Application
or	O
vpn	B-Application
,	O
system	O
wide	O
,	O
via	O
3rd	O
party	O
app	O
helpers	O
like	O
Proxifier	O
,	O
or	O
in	O
form	O
of	O
web	B-Application
browser	I-Application
extension	O
.	O
</s>
<s>
However	O
most	O
extensions	O
in	O
Chrome	B-Application
or	O
Firefox	B-Application
will	O
report	O
false	O
positive	O
working	O
condition	O
even	O
if	O
they	O
did	O
not	O
connect	O
,	O
so	O
3rd	O
party	O
website	O
for	O
ip	O
and	O
dns	B-Application
leak	I-Application
check	O
is	O
recommended	O
.	O
</s>
<s>
This	O
false	O
working	O
state	O
usually	O
happens	O
when	O
two	O
proxy	B-Application
or	O
vpn	B-Application
extensions	O
are	O
tried	O
to	O
be	O
used	O
at	O
the	O
same	O
time	O
(	O
e.g.	O
</s>
<s>
Windscribe	O
VPN	B-Application
and	O
FoxyProxy	O
extensions	O
)	O
.	O
</s>
