<s>
In	O
computing	O
,	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
(	O
also	O
called	O
rabbit	B-Operating_System
virus	I-Operating_System
or	O
wabbit	B-Operating_System
)	O
is	O
a	O
denial-of-service	O
attack	O
wherein	O
a	O
process	B-Operating_System
continually	O
replicates	O
itself	O
to	O
deplete	O
available	O
system	O
resources	O
,	O
slowing	O
down	O
or	O
crashing	O
the	O
system	O
due	O
to	O
resource	B-Operating_System
starvation	I-Operating_System
.	O
</s>
<s>
Around	O
1978	O
,	O
an	O
early	O
variant	O
of	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
called	O
wabbit	B-Operating_System
was	O
reported	O
to	O
run	O
on	O
a	O
System/360	B-Application
.	O
</s>
<s>
It	O
may	O
have	O
descended	O
from	O
a	O
similar	O
attack	O
called	O
RABBITS	B-Operating_System
reported	O
from	O
1969	O
on	O
a	O
Burroughs	B-Device
5500	I-Device
at	O
the	O
University	O
of	O
Washington	O
.	O
</s>
<s>
Fork	B-Operating_System
bombs	I-Operating_System
operate	O
both	O
by	O
consuming	O
CPU	O
time	O
in	O
the	O
process	B-Operating_System
of	O
forking	B-Language
,	O
and	O
by	O
saturating	O
the	O
operating	B-General_Concept
system	I-General_Concept
's	O
process	B-Operating_System
table	I-Operating_System
.	O
</s>
<s>
A	O
basic	O
implementation	O
of	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
is	O
an	O
infinite	B-Algorithm
loop	I-Algorithm
that	O
repeatedly	O
launches	O
new	O
copies	O
of	O
itself	O
.	O
</s>
<s>
In	O
Unix-like	O
operating	B-General_Concept
systems	I-General_Concept
,	O
fork	B-Operating_System
bombs	I-Operating_System
are	O
generally	O
written	O
to	O
use	O
the	O
fork	B-Language
system	B-Operating_System
call	I-Operating_System
.	O
</s>
<s>
As	O
forked	O
processes	O
are	O
also	O
copies	O
of	O
the	O
first	O
program	O
,	O
once	O
they	O
resume	O
execution	O
from	O
the	O
next	O
address	O
at	O
the	O
frame	O
pointer	O
,	O
they	O
continue	O
forking	B-Language
endlessly	O
within	O
their	O
own	O
copy	O
of	O
the	O
same	O
infinite	B-Algorithm
loop	I-Algorithm
;	O
this	O
has	O
the	O
effect	O
of	O
causing	O
an	O
exponential	O
growth	O
in	O
processes	O
.	O
</s>
<s>
As	O
modern	O
Unix	B-Application
systems	I-Application
generally	O
use	O
a	O
copy-on-write	B-Language
resource	O
management	O
technique	O
when	O
forking	B-Language
new	O
processes	O
,	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
generally	O
will	O
not	O
saturate	O
such	O
a	O
system	O
's	O
memory	O
.	O
</s>
<s>
Microsoft	B-Application
Windows	I-Application
operating	I-Application
systems	I-Application
do	O
not	O
have	O
an	O
equivalent	O
functionality	O
to	O
the	O
Unix	B-Application
fork	B-Language
system	B-Operating_System
call	I-Operating_System
;	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
on	O
such	O
an	O
operating	B-General_Concept
system	I-General_Concept
must	O
therefore	O
create	O
a	O
new	O
process	B-Operating_System
instead	O
of	O
forking	B-Language
from	O
an	O
existing	O
one	O
.	O
</s>
<s>
In	O
it	O
,	O
a	O
function	O
is	O
defined	O
(fork( )	O
)	O
as	O
calling	O
itself	O
(	O
fork	B-Language
)	O
,	O
then	O
piping	B-Operating_System
( |	O
)	O
its	O
result	O
to	O
a	O
background	O
job	B-Operating_System
of	O
itself	O
( &	O
)	O
.	O
</s>
<s>
However	O
,	O
its	O
usage	O
is	O
allowed	O
in	O
GNU	B-Operating_System
Bash	I-Operating_System
as	O
an	O
extension	O
.	O
</s>
<s>
The	O
first	O
formulation	O
of	O
the	O
Unix	B-Application
shell	I-Application
fork	B-Operating_System
bomb	I-Operating_System
has	O
been	O
proposed	O
as	O
an	O
anonymous	O
work	O
of	O
art	O
.	O
</s>
<s>
As	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
's	O
mode	O
of	O
operation	O
is	O
entirely	O
encapsulated	O
by	O
creating	O
new	O
processes	O
,	O
one	O
way	O
of	O
preventing	O
a	O
fork	B-Operating_System
bomb	I-Operating_System
from	O
severely	O
affecting	O
the	O
entire	O
system	O
is	O
to	O
limit	O
the	O
maximum	O
number	O
of	O
processes	O
that	O
a	O
single	O
user	O
may	O
own	O
.	O
</s>
<s>
On	O
PAM-enabled	O
systems	O
,	O
this	O
limit	O
can	O
also	O
be	O
set	O
in	O
/etc/security/limits.conf	O
,	O
</s>
<s>
Modern	O
Linux	O
systems	O
also	O
allow	O
finer-grained	O
fork	B-Operating_System
bomb	I-Operating_System
prevention	O
through	O
cgroups	B-Application
and	O
process	B-Operating_System
number	O
(	O
PID	O
)	O
controllers	O
.	O
</s>
