<s>
Parasitic	B-Operating_System
computing	I-Operating_System
is	O
programming	O
technique	O
where	O
a	O
program	O
in	O
normal	O
authorized	O
interactions	O
with	O
another	O
program	O
manages	O
to	O
get	O
the	O
other	O
program	O
to	O
perform	O
computations	O
of	O
a	O
complex	O
nature	O
.	O
</s>
<s>
It	O
is	O
,	O
in	O
a	O
sense	O
,	O
a	O
security	O
exploit	O
in	O
that	O
the	O
program	O
implementing	O
the	O
parasitic	B-Operating_System
computing	I-Operating_System
has	O
no	O
authority	O
to	O
consume	O
resources	O
made	O
available	O
to	O
the	O
other	O
program	O
.	O
</s>
<s>
Each	O
of	O
these	O
smaller	O
problems	O
is	O
then	O
encoded	O
as	O
a	O
relation	O
between	O
a	O
checksum	B-Algorithm
and	O
a	O
packet	B-Protocol
such	O
that	O
whether	O
the	O
checksum	B-Algorithm
is	O
accurate	O
or	O
not	O
is	O
also	O
the	O
answer	O
to	O
that	O
smaller	O
problem	O
.	O
</s>
<s>
The	O
packet/checksum	O
is	O
then	O
sent	O
to	O
another	O
computer	O
.	O
</s>
<s>
This	O
computer	O
will	O
,	O
as	O
part	O
of	O
receiving	O
the	O
packet	B-Protocol
and	O
deciding	O
whether	O
it	O
is	O
valid	O
and	O
well-formed	B-General_Concept
,	O
create	O
a	O
checksum	B-Algorithm
of	O
the	O
packet	B-Protocol
and	O
see	O
whether	O
it	O
is	O
identical	O
to	O
the	O
provided	O
checksum	B-Algorithm
.	O
</s>
<s>
If	O
the	O
checksum	B-Algorithm
is	O
invalid	O
,	O
it	O
will	O
then	O
request	O
a	O
new	O
packet	B-Protocol
from	O
the	O
original	O
computer	O
.	O
</s>
<s>
The	O
original	O
computer	O
now	O
knows	O
the	O
answer	O
to	O
that	O
smaller	O
problem	O
based	O
on	O
the	O
second	O
computer	O
's	O
response	O
,	O
and	O
can	O
transmit	O
a	O
fresh	O
packet	B-Protocol
embodying	O
a	O
different	O
sub-problem	O
.	O
</s>
<s>
The	O
example	O
is	O
based	O
on	O
an	O
exploit	O
of	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
TCP	O
)	O
,	O
used	O
for	O
internet	O
connections	O
,	O
so	O
in	O
the	O
end	O
,	O
the	O
target	O
computer(s )	O
is	O
unaware	O
that	O
it	O
has	O
performed	O
computation	O
for	O
the	O
benefit	O
of	O
the	O
other	O
computer	O
,	O
or	O
even	O
done	O
anything	O
besides	O
have	O
a	O
normal	O
TCP/IP	B-Protocol
session	O
.	O
</s>
<s>
The	O
proof-of-concept	O
is	O
obviously	O
extremely	O
inefficient	O
as	O
the	O
amount	O
of	O
computation	O
necessary	O
to	O
merely	O
send	O
the	O
packets	B-Protocol
in	O
the	O
first	O
place	O
easily	O
exceeds	O
the	O
computations	O
leeched	O
from	O
the	O
other	O
program	O
;	O
the	O
3-SAT	O
problem	O
would	O
be	O
solved	O
much	O
more	O
quickly	O
if	O
just	O
analyzed	O
locally	O
.	O
</s>
<s>
In	O
addition	O
,	O
in	O
practice	O
packets	B-Protocol
would	O
probably	O
have	O
to	O
be	O
retransmitted	O
occasionally	O
when	O
real	O
checksum	B-Algorithm
errors	O
and	O
network	O
problems	O
occur	O
.	O
</s>
<s>
However	O
,	O
parasitic	B-Operating_System
computing	I-Operating_System
on	O
the	O
level	O
of	O
checksums	B-Algorithm
is	O
a	O
demonstration	O
of	O
the	O
concept	O
.	O
</s>
<s>
The	O
authors	O
suggest	O
that	O
as	O
one	O
moves	O
up	O
the	O
application	O
stack	O
,	O
there	O
might	O
come	O
a	O
point	O
where	O
there	O
is	O
a	O
net	O
computational	O
gain	O
to	O
the	O
parasite	O
-	O
perhaps	O
one	O
could	O
break	O
down	O
interesting	O
problems	O
into	O
queries	O
of	O
complex	O
cryptographic	B-Protocol
protocols	I-Protocol
using	O
public	B-Application
keys	I-Application
.	O
</s>
<s>
If	O
there	O
was	O
a	O
net	O
gain	O
,	O
one	O
could	O
in	O
theory	O
use	O
a	O
number	O
of	O
control	O
nodes	O
for	O
which	O
many	O
hosts	O
on	O
the	O
Internet	O
form	O
a	O
distributed	B-Architecture
computing	I-Architecture
network	O
completely	O
unawares	O
.	O
</s>
<s>
Students	O
of	O
the	O
University	O
of	O
Applied	O
Sciences	O
,	O
Bern	O
,	O
Switzerland	O
,	O
extended	O
this	O
concept	O
into	O
a	O
programmable	O
virtual	B-Architecture
machine	I-Architecture
in	O
2002	O
.	O
</s>
<s>
In	O
2011	O
,	O
a	O
group	O
of	O
malware	O
programs	O
were	O
noticed	O
by	O
security	O
software	O
vendors	O
,	O
which	O
utilized	O
high	O
performance	O
graphics	B-Architecture
processing	I-Architecture
units	I-Architecture
(	O
GPUs	B-Architecture
)	O
for	O
Bitcoin	O
mining	O
,	O
a	O
chain	O
of	O
computationally	O
intensive	O
tasks	O
to	O
generate	O
cryptocurrency	O
units	O
.	O
</s>
<s>
Powerful	O
GPUs	B-Architecture
on	O
personal	O
computers	O
were	O
originally	O
created	O
mainly	O
for	O
games	O
,	O
but	O
with	O
interfaces	O
like	O
CUDA	B-Architecture
and	O
OpenCL	B-Application
,	O
became	O
usable	O
for	O
general	O
computing	O
tasks	O
,	O
surpassing	O
the	O
performance	O
of	O
a	O
Central	B-General_Concept
Processing	I-General_Concept
Unit	I-General_Concept
(	O
CPU	O
)	O
by	O
multiple	O
times	O
.	O
</s>
<s>
Until	O
then	O
,	O
parasitic	B-Operating_System
computing	I-Operating_System
lacked	O
powerful	O
computing	O
resources	O
and	O
results	O
to	O
easily	O
convert	O
into	O
cash	O
for	O
criminals	O
.	O
</s>
<s>
In	O
January	O
2014	O
,	O
Bitcoin	O
mining	O
malware	O
was	O
distributed	O
through	O
a	O
Java	B-Language
exploit	O
by	O
compromised	O
ads	O
,	O
displayed	O
on	O
the	O
Yahoo	B-Application
website	O
.	O
</s>
<s>
Bitcoin	O
mining	O
by	O
personal	O
computers	O
infected	O
with	O
malware	O
is	O
being	O
challenged	O
by	O
dedicated	O
hardware	O
,	O
such	O
as	O
FPGA	B-Architecture
and	O
ASIC	O
platforms	O
,	O
which	O
are	O
more	O
efficient	O
in	O
terms	O
of	O
power	O
consumption	O
and	O
thus	O
may	O
have	O
lower	O
costs	O
than	O
theft	O
of	O
computing	O
resources	O
.	O
</s>
