<s>
VPNBook	B-Application
is	O
a	O
VPN	B-Application
service	I-Application
offering	O
servers	O
in	O
multiple	O
countries	O
.	O
</s>
<s>
The	O
service	O
connects	O
to	O
a	O
VPN	O
via	O
OpenVPN	B-Language
client	O
or	O
a	O
PPTP	B-Protocol
connection	O
.	O
</s>
<s>
VPNBook	B-Application
can	O
be	O
used	O
to	O
bypass	O
some	O
governmental	O
restrictions	O
.	O
</s>
<s>
The	O
service	O
can	O
be	O
connected	O
to	O
by	O
two	O
ways	O
,	O
by	O
connection	O
via	O
a	O
third-party	O
OpenVPN	B-Language
client	O
or	O
through	O
PPTP	B-Protocol
.	O
</s>
<s>
The	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
iOS	B-Application
,	O
Android	B-Application
,	O
Ubuntu	B-Operating_System
,	O
and	O
Windows	B-Application
operating	I-Application
systems	I-Application
all	O
have	O
PPTP	B-Protocol
support	O
built	O
in	O
.	O
</s>
<s>
The	O
software	O
(	O
OpenVPN	B-Language
clients	O
)	O
can	O
be	O
used	O
also	O
,	O
that	O
provides	O
the	O
protocol	O
stack	O
,	O
file	O
system	O
,	O
and	O
process	O
scheduling	O
.	O
</s>
<s>
OpenVPN	B-Language
uses	O
SSL	O
protocol	O
which	O
is	O
generally	O
more	O
secure	O
than	O
Layer	O
2	O
Tunnel	O
Protocol	O
's	O
PPTP	B-Protocol
.	O
</s>
<s>
In	O
a	O
review	O
done	O
by	O
PC	O
Magazine	O
,	O
it	O
was	O
concluded	O
that	O
the	O
service	O
is	O
a	O
good	O
choice	O
among	O
free	O
VPN	B-Application
services	I-Application
,	O
even	O
though	O
it	O
has	O
certain	O
functionality	O
flaws	O
.	O
</s>
<s>
TechRadar	O
reviewed	O
VPNBook	B-Application
negatively	O
,	O
criticizing	O
its	O
poor	O
performance	O
and	O
lack	O
of	O
desktop	O
and	O
mobile	O
apps	O
.	O
</s>
