<s>
SquidGuard	B-Application
is	O
a	O
URL	O
redirector	O
software	O
,	O
which	O
can	O
be	O
used	O
for	O
content	B-Protocol
control	I-Protocol
of	O
websites	O
users	O
can	O
access	O
.	O
</s>
<s>
It	O
is	O
written	O
as	O
a	O
plug-in	B-Application
for	O
Squid	B-Protocol
and	O
uses	O
blacklists	O
to	O
define	O
sites	O
for	O
which	O
access	O
is	O
redirected	O
.	O
</s>
<s>
SquidGuard	B-Application
must	O
be	O
installed	O
on	O
a	O
Unix	B-Application
or	O
Linux	B-Application
computer	O
such	O
as	O
a	O
server	O
computer	O
.	O
</s>
<s>
The	O
software	O
's	O
filtering	O
extends	O
to	O
all	O
computers	O
in	O
an	O
organization	O
,	O
including	O
Windows	B-Application
and	O
Macintosh	B-Operating_System
computers	O
.	O
</s>
<s>
New	O
features	O
in	O
version	O
1.4	O
included	O
optional	O
authentication	O
via	O
a	O
MySQL	B-Application
database	O
.	O
</s>
<s>
SquidGuard	B-Application
is	O
free	B-Application
software	I-Application
licensed	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
version	O
2	O
.	O
</s>
<s>
It	O
is	O
included	O
in	O
many	O
Linux	B-Application
distributions	I-Application
including	O
Debian	O
,	O
openSUSE	B-Operating_System
and	O
Ubuntu	B-Operating_System
.	O
</s>
<s>
The	O
url	O
filtering	O
capabilities	O
of	O
SquidGuard	B-Application
depend	O
largely	O
on	O
the	O
quality	O
of	O
the	O
Blacklists	O
used	O
with	O
it	O
.	O
</s>
