<s>
Twelve	B-Application
Tricks	I-Application
is	O
a	O
Trojan	O
horse	O
that	O
first	O
appeared	O
around	O
1990	O
.	O
</s>
<s>
The	O
Trojan	O
came	O
in	O
an	O
altered	O
utility	O
file	O
called	O
CORETEST.COM	O
,	O
which	O
was	O
intended	O
to	O
test	O
performance	O
of	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
It	O
affected	O
IBM	O
platform	O
computers	O
running	O
MS-DOS	B-Application
or	O
PC	B-Operating_System
DOS	I-Operating_System
.	O
</s>
<s>
The	O
Trojan	O
alters	O
the	O
master	B-Device
boot	I-Device
record	I-Device
(	O
partition	B-Device
sector	I-Device
)	O
and	O
,	O
at	O
every	O
reboot	O
,	O
it	O
installs	O
one	O
of	O
twelve	O
"	O
tricks	O
"	O
that	O
causes	O
issues	O
with	O
hardware	O
or	O
operation	O
of	O
the	O
computer	O
.	O
</s>
<s>
The	O
trick	O
vanishes	O
when	O
the	O
power	O
is	O
cut	O
off	O
,	O
and	O
any	O
of	O
the	O
twelve	B-Application
tricks	I-Application
may	O
appear	O
or	O
reappear	O
on	O
the	O
next	O
reboot	O
.	O
</s>
<s>
In	O
addition	O
,	O
on	O
each	O
boot	O
the	O
Trojan	O
uses	O
a	O
random	O
number	O
generator	O
to	O
determine	O
whether	O
to	O
do	O
a	O
low-level	O
format	B-Application
of	O
the	O
active	O
copy	O
of	O
the	O
boot	B-Device
sector	I-Device
and	O
the	O
first	O
copy	O
of	O
the	O
FAT	B-Application
;	O
there	O
is	O
a	O
1/4096	O
chance	O
of	O
this	O
happening	O
.	O
</s>
<s>
If	O
the	O
format	B-Application
does	O
not	O
happen	O
,	O
the	O
Trojan	O
randomly	O
changes	O
one	O
random	O
word	O
in	O
any	O
of	O
the	O
first	O
sixteen	O
sectors	O
of	O
the	O
FAT	B-Application
,	O
leading	O
to	O
a	O
gradual	O
corruption	O
of	O
the	O
file	O
system	O
.	O
</s>
