<s>
Ontario	B-Architecture
is	O
a	O
family	O
of	O
computer	O
viruses	O
,	O
named	O
after	O
its	O
point	O
of	O
isolation	O
,	O
the	O
Canadian	O
province	O
of	O
Ontario	B-Architecture
.	O
</s>
<s>
This	O
family	O
of	O
computer	O
virus	O
consists	O
of	O
Ontario.1024	O
,	O
Ontario.512	O
and	O
Ontario.2048	O
.	O
</s>
<s>
The	O
first	O
variant	O
Ontario.512	O
was	O
discovered	O
in	O
July	O
1990	O
.	O
</s>
<s>
Because	O
Ontario.1024	O
was	O
also	O
discovered	O
in	O
Ontario	B-Architecture
,	O
it	O
is	O
likely	O
that	O
both	O
viruses	O
originate	O
from	O
within	O
the	O
province	O
.	O
</s>
<s>
By	O
the	O
Ontario.2048	O
variant	O
,	O
the	O
author	O
had	O
adopted	O
"	O
Ontario	B-Architecture
"	O
as	O
the	O
family	O
's	O
name	O
and	O
even	O
included	O
the	O
name	O
"	O
Ontario-3	O
"	O
in	O
the	O
virus	O
code	O
.	O
</s>
<s>
Ontario.512	O
is	O
an	O
encrypting	O
DOS	B-Device
file	O
infector	O
.	O
</s>
<s>
Upon	O
the	O
execution	O
of	O
an	O
infected	O
.COM	O
,	O
.EXE	O
or	O
.OVL	B-General_Concept
file	O
,	O
Ontario.512	O
goes	O
memory	O
resident	O
and	O
infects	O
files	O
of	O
these	O
times	O
upon	O
being	O
opened	O
.	O
</s>
<s>
COMMAND.COM	B-Operating_System
is	O
infected	O
using	O
a	O
special	O
routine	O
.	O
</s>
<s>
Infected	O
files	O
will	O
increase	O
either	O
512	O
bytes	O
(	O
COM	O
files	O
)	O
or	O
between	O
512	O
and	O
1,023	O
bytes	O
(	O
EXE	O
and	O
OVL	B-General_Concept
files	I-General_Concept
)	O
.	O
</s>
<s>
Ontario.512	O
primarily	O
only	O
infects	O
files	O
,	O
so	O
there	O
is	O
no	O
one	O
significant	O
symptom	O
.	O
</s>
<s>
An	O
increase	O
in	O
size	O
of	O
infected	O
EXE	O
and	O
OVL	B-General_Concept
files	I-General_Concept
of	O
between	O
512	O
and	O
1,023	O
bytes	O
,	O
and	O
even	O
greater	O
on	O
some	O
systems	O
.	O
</s>
<s>
Systems	O
thoroughly	O
infected	O
by	O
Ontario.512	O
may	O
suffer	O
from	O
increasing	O
file	O
corruption	O
and	O
other	O
hard	O
drive	O
problems	O
over	O
time	O
.	O
</s>
<s>
Unspecified	O
printer	O
problems	O
have	O
been	O
observed	O
with	O
the	O
Ontario	B-Architecture
family	O
,	O
although	O
most	O
of	O
these	O
observations	O
have	O
related	O
to	O
Ontario.1024	O
,	O
not	O
Ontario.512	O
.	O
</s>
<s>
It	O
is	O
unknown	O
what	O
specific	O
problems	O
these	O
are	O
,	O
and	O
if	O
they	O
affect	O
Ontario.512	O
.	O
</s>
<s>
The	O
increase	O
in	O
COM	O
file	O
size	O
in	O
conjunction	O
with	O
EXE	O
and	O
OVL	B-General_Concept
file	I-General_Concept
increases	O
is	O
a	O
very	O
good	O
guideline	O
when	O
determining	O
Ontario.512	O
infection	O
,	O
although	O
file	O
length	O
changes	O
are	O
common	O
among	O
virtually	O
every	O
file	O
infector	O
.	O
</s>
<s>
The	O
WildList	O
,	O
an	O
organisation	O
tracking	O
computer	O
viruses	O
,	O
never	O
reported	O
Ontario.512	O
as	O
being	O
in	O
the	O
field	O
.	O
</s>
<s>
However	O
,	O
Ontario.1024	O
was	O
included	O
on	O
the	O
list	O
for	O
a	O
period	O
of	O
time	O
.	O
</s>
<s>
It	O
is	O
unclear	O
whether	O
Ontario.512	O
was	O
discovered	O
in	O
the	O
field	O
,	O
or	O
off	O
a	O
BBS	B-Application
out	O
of	O
Toronto	O
,	O
where	O
Ontario.2048	O
was	O
posted	O
.	O
</s>
<s>
Ontario.1024	O
is	O
a	O
computer	O
virus	O
,	O
discovered	O
in	O
October	O
1991	O
,	O
over	O
a	O
year	O
after	O
the	O
isolation	O
of	O
the	O
first	O
Ontario	B-Architecture
virus	O
,	O
Ontario.512	O
.	O
</s>
<s>
Relative	O
to	O
Ontario.512	O
,	O
most	O
additions	O
involve	O
making	O
the	O
virus	O
harder	O
to	O
detect	O
.	O
</s>
<s>
Ontario.1024	O
is	O
an	O
encrypting	O
,	O
stealth	O
DOS	B-Device
file	O
infector	O
.	O
</s>
<s>
Upon	O
the	O
execution	O
of	O
an	O
infected	O
.COM	O
or	O
.EXE	O
file	O
,	O
Ontario.1024	O
goes	O
memory	O
resident	O
and	O
infects	O
files	O
of	O
these	O
types	O
upon	O
being	O
opened	O
.	O
</s>
<s>
COMMAND.COM	B-Operating_System
is	O
infected	O
using	O
a	O
special	O
routine	O
.	O
</s>
<s>
However	O
,	O
when	O
Ontario.1024	O
is	O
in	O
memory	O
,	O
no	O
increase	O
in	O
file	O
size	O
will	O
be	O
observed	O
due	O
to	O
the	O
virus	O
 '	O
stealthing	O
.	O
</s>
<s>
Unlike	O
Ontario.512	O
,	O
it	O
will	O
not	O
infect	O
.OVL	B-General_Concept
files	O
.	O
</s>
<s>
Ontario.1024	O
is	O
the	O
least	O
readily	O
identified	O
version	O
of	O
the	O
Ontario	B-Architecture
family	O
.	O
</s>
<s>
The	O
first	O
three	O
symptoms	O
are	O
good	O
indications	O
that	O
a	O
virus	O
is	O
present	O
,	O
but	O
are	O
not	O
necessarily	O
specific	O
to	O
Ontario.1024	O
.	O
</s>
<s>
The	O
WildList	O
,	O
an	O
organisation	O
tracking	O
computer	O
viruses	O
,	O
listed	O
Ontario.1024	O
as	O
being	O
in	O
the	O
field	O
from	O
July	O
1993	O
to	O
December	O
1998	O
,	O
when	O
it	O
was	O
removed	O
due	O
to	O
lack	O
of	O
a	O
submitted	O
sample	O
.	O
</s>
<s>
These	O
reports	O
indicated	O
that	O
Ontario.1024	O
had	O
spread	O
as	O
widely	O
as	O
Australia	O
and	O
Israel	O
at	O
its	O
peak	O
in	O
1994-1995	O
.	O
</s>
<s>
Like	O
all	O
DOS	B-Device
file	O
infectors	O
,	O
the	O
advent	O
of	O
Windows	B-Application
significantly	O
hindered	O
the	O
spread	O
of	O
Ontario.1024	O
.	O
</s>
<s>
It	O
is	O
the	O
third	O
and	O
final	O
known	O
variant	O
of	O
the	O
Ontario	B-Architecture
family	O
,	O
both	O
chronologically	O
and	O
in	O
complexity	O
.	O
</s>
<s>
Ontario.2048	O
is	O
an	O
encrypting	O
,	O
polymorphic	O
,	O
stealth	O
DOS	B-Device
file	O
infector	O
.	O
</s>
<s>
Upon	O
the	O
execution	O
of	O
an	O
infected	O
.COM	O
,	O
.EXE	O
,	O
.OVL	B-General_Concept
,	O
or	O
.SYS	O
file	O
,	O
Ontario.2048	O
goes	O
memory	O
resident	O
and	O
infects	O
files	O
of	O
these	O
times	O
upon	O
being	O
opened	O
.	O
</s>
<s>
COMMAND.COM	B-Operating_System
is	O
infected	O
using	O
a	O
special	O
routine	O
,	O
and	O
will	O
not	O
increase	O
in	O
file	O
size	O
.	O
</s>
<s>
However	O
,	O
when	O
Ontario.2048	O
is	O
in	O
memory	O
,	O
no	O
increase	O
in	O
file	O
size	O
will	O
be	O
observed	O
due	O
to	O
the	O
virus	O
 '	O
stealthing	O
.	O
</s>
<s>
When	O
the	O
DOS	B-Device
DEBUG	I-Device
program	O
is	O
in	O
memory	O
,	O
Ontario.2048	O
will	O
detect	O
it	O
and	O
disinfect	O
programs	O
in	O
memory	O
to	O
avoid	O
being	O
analysed	O
.	O
</s>
<s>
Ontario.2048	O
also	O
features	O
an	O
extremely	O
complex	O
encryption	O
system	O
;	O
a	O
given	O
sample	O
of	O
Ontario.2048	O
may	O
only	O
share	O
two	O
bytes	O
in	O
common	O
with	O
another	O
.	O
</s>
<s>
Ontario.2048	O
can	O
result	O
in	O
the	O
following	O
symptoms	O
:	O
</s>
<s>
Occasional	O
printer-related	O
problems	O
have	O
been	O
observed	O
in	O
the	O
Ontario.1024	O
variant	O
of	O
this	O
family	O
;	O
it	O
is	O
unknown	O
whether	O
this	O
carries	O
over	O
to	O
Ontario.2048	O
.	O
</s>
<s>
The	O
first	O
three	O
symptoms	O
are	O
good	O
indications	O
that	O
a	O
virus	O
is	O
present	O
,	O
but	O
are	O
not	O
necessarily	O
specific	O
to	O
Ontario.1024	O
.	O
</s>
<s>
Ontario.2048	O
also	O
contains	O
text	O
,	O
which	O
is	O
invisible	O
because	O
Ontario.2048	O
is	O
encrypted	O
.	O
</s>
<s>
The	O
first	O
line	O
is	O
a	O
reference	O
to	O
the	O
method	O
used	O
to	O
find	O
COMMAND.COM	B-Operating_System
to	O
infect	O
,	O
as	O
well	O
as	O
file	O
types	O
that	O
the	O
virus	O
infects	O
.	O
</s>
<s>
The	O
second	O
line	O
refers	O
to	O
the	O
version	O
of	O
MS-DOS	B-Application
that	O
Ontario.2048	O
was	O
written	O
on	O
.	O
</s>
<s>
A	O
number	O
of	O
descriptions	O
note	O
multipartite	O
function	O
in	O
Ontario.2048	O
.	O
</s>
<s>
Ontario.2048	O
does	O
contain	O
a	O
boot	O
sector	O
within	O
it	O
with	O
a	O
boot	O
virus	O
.	O
</s>
<s>
If	O
inserted	O
into	O
the	O
boot	O
sector	O
,	O
it	O
would	O
be	O
a	O
functioning	O
boot	O
virus	O
(	O
although	O
it	O
would	O
not	O
spread	O
the	O
file	O
infection	O
portion	O
of	O
Ontario.2048	O
)	O
.	O
</s>
<s>
However	O
,	O
Ontario.2048	O
never	O
performs	O
the	O
injection	O
;	O
the	O
code	O
is	O
functionally	O
useless	O
.	O
</s>
<s>
The	O
WildList	O
,	O
an	O
organisation	O
tracking	O
computer	O
viruses	O
,	O
has	O
never	O
listed	O
Ontario.2048	O
as	O
being	O
in	O
the	O
field	O
.	O
</s>
<s>
However	O
,	O
Ontario.1024	O
was	O
included	O
for	O
a	O
period	O
of	O
time	O
.	O
</s>
<s>
Like	O
all	O
DOS	B-Device
file	O
infectors	O
,	O
the	O
advent	O
of	O
Windows	B-Application
significantly	O
hindered	O
the	O
spread	O
of	O
Ontario.2048	O
.	O
</s>
