<s>
A	O
network	B-Protocol
telescope	I-Protocol
(	O
also	O
known	O
as	O
a	O
packet	O
telescope	O
,	O
darknet	O
,	O
Internet	O
motion	O
sensor	O
or	O
black	O
hole	O
)	O
is	O
an	O
Internet	O
system	O
that	O
allows	O
one	O
to	O
observe	O
different	O
large-scale	O
events	O
taking	O
place	O
on	O
the	O
Internet	O
.	O
</s>
<s>
The	O
resolution	O
of	O
the	O
Internet	B-Protocol
telescope	I-Protocol
is	O
dependent	O
on	O
the	O
number	O
of	O
IP	B-Protocol
addresses	I-Protocol
it	O
monitors	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
large	O
Internet	B-Protocol
telescope	I-Protocol
that	O
monitors	O
traffic	O
to	O
16,777,216	O
addresses	O
(	O
the	O
Internet	B-Protocol
telescope	I-Protocol
in	O
IPv4	B-Protocol
)	O
,	O
has	O
a	O
higher	O
probability	O
of	O
observing	O
a	O
relatively	O
small	O
event	O
than	O
a	O
smaller	O
telescope	O
that	O
monitors	O
65,536	O
addresses	O
(	O
a	O
Internet	B-Protocol
telescope	I-Protocol
)	O
.	O
</s>
<s>
The	O
naming	O
comes	O
from	O
an	O
analogy	O
to	O
optical	O
telescopes	O
,	O
where	O
a	O
larger	O
physical	O
size	O
allows	O
more	O
photons	B-Application
to	O
be	O
observed	O
.	O
</s>
<s>
A	O
variant	O
of	O
a	O
network	B-Protocol
telescope	I-Protocol
is	O
a	O
sparse	O
darknet	O
,	O
or	O
greynet	O
,	O
consisting	O
of	O
a	O
region	O
of	O
IP	B-Protocol
address	I-Protocol
space	O
that	O
is	O
sparsely	O
populated	O
with	O
"	O
darknet	O
"	O
addresses	O
interspersed	O
with	O
active	O
(	O
or	O
"	O
lit	O
"	O
)	O
IP	B-Protocol
addresses	I-Protocol
.	O
</s>
<s>
These	O
include	O
a	O
greynet	O
assembled	O
from	O
210,000	O
unused	O
IP	B-Protocol
addresses	I-Protocol
mainly	O
located	O
in	O
Japan	O
.	O
</s>
