<s>
Clickbot.A	B-Protocol
is	O
a	O
botnet	B-Architecture
that	O
is	O
used	O
for	O
click	O
fraud	O
.	O
</s>
<s>
The	O
bot	O
was	O
first	O
discovered	O
by	O
Swa	O
Frantzen	O
at	O
SANS	O
 '	O
Internet	B-Application
Storm	I-Application
Center	I-Application
in	O
May	O
2006	O
.	O
</s>
<s>
At	O
that	O
time	O
,	O
the	O
botnet	B-Architecture
had	O
infected	O
about	O
100	O
machines	O
.	O
</s>
<s>
The	O
bot	O
was	O
written	O
as	O
a	O
plugin	O
to	O
Internet	B-Application
Explorer	I-Application
that	O
was	O
downloaded	O
by	O
IE	O
users	O
.	O
</s>
