<s>
KoKo	B-Application
Virus	O
is	O
a	O
memory	O
resident	O
computer	O
virus	O
created	O
in	O
March	O
1991	O
.	O
</s>
<s>
KoKo	B-Application
's	O
name	O
came	O
from	O
the	O
creator	O
himself	O
,	O
which	O
was	O
a	O
nickname	O
used	O
by	O
his	O
friends	O
.	O
</s>
<s>
Many	O
on-line	O
virus	O
databases	O
refer	O
to	O
KoKo	B-Application
as	O
Koko.1780	O
.	O
</s>
<s>
KoKo	B-Application
is	O
written	O
in	O
the	O
Assembly	B-Language
programming	I-Language
language	I-Language
and	O
the	O
executable	O
file	O
usually	O
has	O
an	O
approximate	O
file	O
size	O
of	O
around	O
1780	O
bytes	B-Application
.	O
</s>
<s>
The	O
KoKo	B-Application
virus	O
infects	O
the	O
target	O
system	O
by	O
hooking	O
the	O
Windows	O
interrupt	O
INT	B-Application
21h	I-Application
and	O
writes	O
itself	O
to	O
the	O
end	O
of	O
COM	O
and	O
EXE	O
files	O
that	O
are	O
executed	O
.	O
</s>
<s>
When	O
activated	O
the	O
virus	O
displays	O
a	O
message	O
and	O
may	O
erase	O
the	O
computers	O
disk	B-Application
sectors	I-Application
.	O
</s>
<s>
KoKo	B-Application
is	O
Sleeping	O
in	O
Your	O
PC	O
.	O
</s>
