<s>
In	O
operating	B-General_Concept
systems	I-General_Concept
architecture	O
a	O
reference	B-Application
monitor	I-Application
concept	O
defines	O
a	O
set	O
of	O
design	O
requirements	O
on	O
a	O
reference	O
validation	O
mechanism	O
,	O
which	O
enforces	O
an	O
access	O
control	O
policy	O
over	O
subjects	O
 '	O
(	O
e.g.	O
,	O
processes	O
and	O
users	O
)	O
ability	O
to	O
perform	O
operations	O
(	O
e.g.	O
,	O
read	O
and	O
write	O
)	O
on	O
objects	O
(	O
e.g.	O
,	O
files	O
and	O
sockets	O
)	O
on	O
a	O
system	O
.	O
</s>
<s>
The	O
properties	O
of	O
a	O
reference	B-Application
monitor	I-Application
are	O
captured	O
by	O
the	O
acronym	O
NEAT	O
,	O
which	O
means	O
:	O
</s>
<s>
For	O
example	O
,	O
Windows	B-Application
3.x	I-Application
and	O
9x	O
operating	B-General_Concept
systems	I-General_Concept
were	O
not	O
built	O
with	O
a	O
reference	B-Application
monitor	I-Application
,	O
whereas	O
the	O
Windows	B-Device
NT	I-Device
line	O
,	O
which	O
also	O
includes	O
Windows	B-Application
2000	I-Application
and	O
Windows	B-Application
XP	I-Application
,	O
was	O
designed	O
to	O
contain	O
a	O
reference	B-Application
monitor	I-Application
,	O
although	O
it	O
is	O
not	O
clear	O
that	O
its	O
properties	O
(	O
tamperproof	O
,	O
etc	O
.	O
)	O
</s>
<s>
The	O
claim	O
is	O
that	O
a	O
reference	O
validation	O
mechanism	O
that	O
satisfies	O
the	O
reference	B-Application
monitor	I-Application
concept	O
will	O
correctly	O
enforce	O
a	O
system	O
's	O
access	O
control	O
policy	O
,	O
as	O
it	O
must	O
be	O
invoked	O
to	O
mediate	O
all	O
security-sensitive	O
operations	O
,	O
must	O
not	O
be	O
tampered	O
with	O
,	O
and	O
has	O
undergone	O
complete	O
analysis	O
and	O
testing	O
to	O
verify	O
correctness	O
.	O
</s>
<s>
The	O
abstract	O
model	O
of	O
a	O
reference	B-Application
monitor	I-Application
has	O
been	O
widely	O
applied	O
to	O
any	O
type	O
of	O
system	O
that	O
needs	O
to	O
enforce	O
access	O
control	O
and	O
is	O
considered	O
to	O
express	O
the	O
necessary	O
and	O
sufficient	O
properties	O
for	O
any	O
system	O
making	O
this	O
security	O
claim	O
.	O
</s>
<s>
According	O
to	O
Ross	O
Anderson	O
,	O
the	O
reference	B-Application
monitor	I-Application
concept	O
was	O
introduced	O
by	O
James	O
Anderson	O
in	O
an	O
influential	O
1972	O
paper	O
.	O
</s>
<s>
Systems	O
evaluated	O
at	O
B3	O
and	O
above	O
by	O
the	O
Trusted	O
Computer	O
System	O
Evaluation	O
Criteria	O
(	O
TCSEC	O
)	O
must	O
enforce	O
the	O
reference	B-Application
monitor	I-Application
concept	O
.	O
</s>
