<s>
Killbit	B-Application
is	O
a	O
security	O
feature	O
in	O
web	O
browsers	O
based	O
on	O
Microsoft	O
's	O
Trident	B-Application
engine	I-Application
(	O
such	O
as	O
Internet	B-Application
Explorer	I-Application
)	O
and	O
other	O
ActiveX	B-Application
containers	O
that	O
respect	O
the	O
killbit	B-Application
(	O
such	O
as	O
Microsoft	B-Application
Office	I-Application
)	O
.	O
</s>
<s>
A	O
killbit	B-Application
instructs	O
an	O
ActiveX	B-Application
control	I-Application
container	O
never	O
to	O
use	O
a	O
specific	O
piece	O
of	O
ActiveX	B-Application
software	O
,	O
whether	O
third-party	O
or	O
Microsoft	O
,	O
as	O
identified	O
by	O
its	O
class	O
identifier	O
(	O
CLSID	O
)	O
.	O
</s>
<s>
The	O
main	O
purpose	O
of	O
a	O
killbit	B-Application
is	O
to	O
close	O
security	O
holes	O
.	O
</s>
<s>
If	O
a	O
vendor	O
discovers	O
that	O
there	O
is	O
a	O
security	O
hole	O
in	O
a	O
specific	O
version	O
of	O
an	O
ActiveX	B-Application
control	I-Application
,	O
they	O
can	O
request	O
that	O
Microsoft	O
put	O
out	O
a	O
"	O
killbit	B-Application
"	O
for	O
it	O
.	O
</s>
<s>
Killbit	B-Application
updates	O
are	O
typically	O
deployed	O
to	O
Microsoft	B-Application
Windows	I-Application
operating	I-Application
systems	I-Application
via	O
Windows	O
Update	O
.	O
</s>
<s>
A	O
flag	O
in	O
the	O
Windows	B-Protocol
Registry	I-Protocol
identifies	O
a	O
CLSID	O
as	O
unsafe	O
.	O
</s>
<s>
It	O
must	O
exist	O
for	O
each	O
piece	O
of	O
software	O
that	O
behaves	O
as	O
an	O
ActiveX	B-Application
control	I-Application
.	O
</s>
<s>
If	O
an	O
ActiveX	B-Application
container	O
finds	O
that	O
the	O
CLSID	O
of	O
a	O
killbit	B-Application
entry	O
matches	O
the	O
CLSID	O
of	O
the	O
software	O
,	O
the	O
software	O
is	O
blocked	O
from	O
running	O
in	O
the	O
ActiveX	B-Application
container	O
.	O
</s>
<s>
Internet	B-Application
Explorer	I-Application
's	O
HTML	B-Application
application	I-Application
host	O
also	O
respects	O
the	O
killbit	B-Application
when	O
processing	O
the	O
OBJECT	O
tag	O
in	O
HTML	O
,	O
but	O
not	O
when	O
processing	O
scripts	O
in	O
HTML	O
.	O
</s>
