<s>
Westwood	B-Application
is	O
a	O
computer	O
virus	O
,	O
a	O
variant	O
of	O
the	O
Jerusalem	B-Application
family	O
,	O
discovered	O
August	O
1990	O
,	O
in	O
Westwood	B-Application
,	O
Los	O
Angeles	O
,	O
California	O
.	O
</s>
<s>
Westwood	B-Application
was	O
an	O
early	O
variant	O
of	O
the	O
Jerusalem	B-Application
virus	I-Application
,	O
which	O
was	O
the	O
first	O
DOS	B-Device
file	O
infector	O
to	O
become	O
common	O
.	O
</s>
<s>
Upon	O
execution	O
of	O
an	O
infected	O
file	O
,	O
Westwood	B-Application
becomes	O
memory	O
resident	O
.	O
</s>
<s>
Any	O
file	O
of	O
COM	O
,	O
EXE	O
,	O
or	O
OVL	B-General_Concept
types	O
is	O
infected	O
upon	O
execution	O
,	O
except	O
COMMAND.COM	B-Operating_System
.	O
</s>
<s>
A	O
number	O
of	O
symptoms	O
are	O
associated	O
with	O
Westwood	B-Application
:	O
</s>
<s>
COM	O
files	O
executed	O
will	O
increase	O
by	O
1,829	O
bytes	O
in	O
size	O
;	O
EXE	O
and	O
OVL	B-General_Concept
files	I-General_Concept
will	O
increase	O
by	O
between	O
1,819	O
and	O
1,829	O
bytes	O
.	O
</s>
<s>
Interrupts	B-Application
8	O
and	O
21	O
will	O
be	O
hooked	O
;	O
on	O
Friday	B-Device
the	I-Device
13th	I-Device
,	O
interrupt	B-Application
22	O
will	O
also	O
be	O
hooked	O
.	O
</s>
<s>
Thirty	O
minutes	O
after	O
the	O
virus	O
goes	O
memory	O
resident	O
,	O
the	O
system	O
will	O
slow	O
down	O
,	O
and	O
a	O
small	O
black	O
box	O
will	O
appear	O
in	O
the	O
bottom	O
left-hand	O
corner	O
of	O
the	O
machine	O
,	O
as	O
common	O
among	O
most	O
Jerusalem	B-Application
variants	O
.	O
</s>
<s>
These	O
symptoms	O
are	O
not	O
indicative	O
of	O
a	O
Westwood	B-Application
infection	O
,	O
although	O
the	O
final	O
symptom	O
is	O
certainly	O
not	O
regular	O
program	O
behaviour	O
,	O
and	O
any	O
automatic	O
file	O
size	O
increase	O
of	O
executables	O
is	O
suspicious	O
.	O
</s>
<s>
The	O
infection	O
mechanism	O
in	O
Westwood	B-Application
is	O
better-written	O
than	O
the	O
original	O
Jerusalem	B-Application
's	O
.	O
</s>
<s>
Westwood	B-Application
infects	O
only	O
once	O
.	O
</s>
<s>
As	O
with	O
most	O
Jerusalem	B-Application
variants	O
,	O
Westwood	B-Application
contains	O
a	O
destructive	O
payload	O
.	O
</s>
<s>
On	O
every	O
Friday	B-Device
the	I-Device
13th	I-Device
,	O
interrupt	B-Application
22	O
will	O
be	O
hooked	O
.	O
</s>
<s>
Westwood	B-Application
is	O
functionally	O
similar	O
to	O
Jerusalem	B-Application
,	O
but	O
the	O
coding	O
is	O
quite	O
different	O
in	O
many	O
areas	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
virus	O
removal	O
signatures	O
used	O
to	O
detect	O
the	O
original	O
Jerusalem	B-Application
had	O
to	O
be	O
modified	O
to	O
detect	O
Westwood	B-Application
.	O
</s>
<s>
Organisations	O
such	O
as	O
Virus	O
Bulletin	O
used	O
to	O
use	O
Westwood	B-Application
to	O
test	O
virus	O
scanners	O
for	O
ability	O
to	O
distinguish	O
Jerusalem	B-Application
variants	O
.	O
</s>
<s>
The	O
WildList	O
,	O
an	O
organization	O
tracking	O
computer	O
viruses	O
,	O
never	O
reported	O
Westwood	B-Application
as	O
being	O
in	O
the	O
field	O
.	O
</s>
<s>
However	O
,	O
its	O
isolation	O
was	O
made	O
after	O
the	O
virus	O
had	O
made	O
infections	O
in	O
the	O
community	O
of	O
Westwood	B-Application
.	O
</s>
<s>
It	O
is	O
unknown	O
how	O
much	O
Westwood	B-Application
spread	O
outside	O
California	O
(	O
with	O
a	O
few	O
reports	O
in	O
neighbouring	O
states	O
)	O
,	O
especially	O
as	O
Westwood	B-Application
is	O
easily	O
mis-diagnosed	O
as	O
Jerusalem	B-Application
.	O
</s>
<s>
Since	O
the	O
advent	O
of	O
Windows	B-Application
,	O
even	O
successful	O
Jerusalem	B-Application
variants	O
have	O
become	O
increasingly	O
uncommon	O
.	O
</s>
<s>
As	O
such	O
,	O
Westwood	B-Application
is	O
considered	O
obsolete	O
.	O
</s>
