<s>
An	O
algorithmic	B-General_Concept
complexity	I-General_Concept
attack	I-General_Concept
(	O
ACA	O
)	O
is	O
a	O
form	O
of	O
attack	O
in	O
which	O
the	O
system	O
is	O
attacked	O
by	O
an	O
exhaustion	O
resource	O
to	O
take	O
advantage	O
of	O
worst-case	B-General_Concept
performance	I-General_Concept
.	O
</s>
<s>
Worst-case	B-General_Concept
performance	I-General_Concept
through	O
a	O
back-end	O
algorithm	O
results	O
in	O
the	O
exhaustion	O
of	O
the	O
server	O
,	O
this	O
creates	O
algorithmic	O
complexity	O
vulnerabilities	O
.	O
</s>
<s>
Examples	O
of	O
ACA	O
attacks	O
are	O
zip-bombs	O
,	O
billion	O
laughs	O
,	O
and	O
ReDoS	O
which	O
are	O
Malicious	O
files	O
aimed	O
to	O
render	O
a	O
program	O
useless	O
.	O
</s>
<s>
In	O
October	O
2022	O
,	O
Google	B-Application
released	O
that	O
they	O
experienced	O
the	O
largest	O
DDoS	O
attack	O
to	O
date	O
that	O
took	O
place	O
in	O
September	O
2017	O
.	O
</s>
<s>
While	O
the	O
front-end	O
part	O
of	O
the	O
algorithm	O
is	O
the	O
part	O
of	O
the	O
website	O
users	O
can	O
see	O
and	O
interact	O
with	O
such	O
as	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
,	O
the	O
back-end	O
aspect	O
are	O
the	O
lines	O
of	O
code	O
behind	O
the	O
project	O
.	O
</s>
<s>
Additionally	O
,	O
Allen	O
Tucker	O
,	O
a	O
computer	O
science	O
professor	O
at	O
Bowdoin	O
College	O
,	O
stated	O
"	O
Computational	O
complexity	O
is	O
a	O
continuum	O
,	O
in	O
that	O
some	O
algorithms	O
require	O
linear	O
time	O
(	O
that	O
is	O
,	O
the	O
time	O
required	O
increases	O
directly	O
with	O
the	O
number	O
of	O
items	O
or	O
nodes	O
in	O
the	O
list	O
,	O
graph	O
,	O
or	O
network	O
being	O
processed	O
)	O
,	O
whereas	O
others	O
require	O
quadratic	O
or	O
even	O
exponential	O
time	O
to	O
complete	O
"	O
As	O
previously	O
stated	O
,	O
although	O
there	O
are	O
multiple	O
ways	O
to	O
create	O
a	O
program	O
it	O
is	O
important	O
to	O
be	O
able	O
calculate	O
the	O
efficiency	O
of	O
an	O
algorithm	O
to	O
better	O
classify	O
and	O
make	O
the	O
algorithms	O
run	O
on	O
a	O
best-case	B-General_Concept
scenario	O
.	O
</s>
<s>
Regular	B-Language
expression	I-Language
Denial	O
of	O
Service	O
attacks	O
are	O
a	O
type	O
of	O
DoS	O
in	O
which	O
the	O
attacker	O
uses	O
inputs	O
that	O
take	O
a	O
long	O
time	O
for	O
the	O
computer	O
to	O
evaluate/process	O
to	O
create	O
a	O
denial-of-service	O
error	O
.	O
</s>
<s>
ReDoS	O
attacks	O
take	O
advantage	O
of	O
"	O
evil	O
"	O
aspects	O
of	O
a	O
regular	O
expression(regex )	O
which	O
overloads	O
the	O
server	O
making	O
it	O
inaccessible	O
to	O
its	O
users	O
.	O
</s>
<s>
According	O
to	O
a	O
study	O
by	O
Adar	O
Weidman	O
,	O
a	O
Code	O
Analysis	O
Architect	O
at	O
the	O
,	O
“	O
In	O
every	O
layer	O
of	O
the	O
WEB	O
there	O
are	O
Regular	B-Language
Expressions	I-Language
,	O
that	O
might	O
contain	O
an	O
Evil	O
Regex	B-Language
.	O
</s>
<s>
An	O
attacker	O
can	O
hang	O
a	O
WEB-browser	O
(	O
on	O
a	O
computer	O
or	O
potentially	O
also	O
on	O
a	O
mobile	O
device	O
)	O
,	O
hang	O
a	O
Web	B-Protocol
Application	I-Protocol
Firewall	I-Protocol
(	O
WAF	O
)	O
,	O
attack	O
a	O
database	O
,	O
and	O
even	O
stack	O
a	O
vulnerable	O
WEB	O
server.	O
”	O
This	O
type	O
of	O
an	O
attack	O
could	O
be	O
costly	O
to	O
big	O
corporations	O
because	O
application	O
outages	O
caused	O
by	O
ReDoS	O
can	O
degrade	O
the	O
operational	O
efficiency	O
,	O
reduced	O
revenues	O
,	O
and	O
damaged	O
the	O
brand	O
reputation	O
.	O
</s>
<s>
Otherwise	O
known	O
as	O
XML	B-Protocol
bombs	O
,	O
these	O
attacks	O
are	O
a	O
form	O
of	O
DDoS	O
attacks	O
that	O
are	O
aimed	O
at	O
parsers	O
of	O
XML	B-Protocol
documents	I-Protocol
.	O
</s>
<s>
For	O
example	O
,	O
XML	B-Protocol
documents	I-Protocol
of	O
e-commerce	O
transactions	O
,	O
server	O
APIs	O
,	O
and	O
customer	O
information	O
can	O
be	O
stolen	O
through	O
XML	B-Protocol
attacks	O
.	O
</s>
<s>
“	O
Documents	O
that	O
include	O
and	O
obey	O
a	O
schema	O
rather	O
than	O
a	O
DTD	B-Language
are	O
considered	O
to	O
be	O
"	O
schema-valid.	O
"	O
</s>
<s>
Schemas	O
are	O
files	O
describing	O
the	O
XML	B-Protocol
document	I-Protocol
and	O
its	O
precise	O
structure.	O
”	O
(	O
Microfocus	O
)	O
According	O
to	O
an	O
article	O
from	O
StackOverflow	B-Error_Name
,	O
a	O
trusted	O
resource	O
for	O
developers	O
,	O
data	O
scientists	O
,	O
and	O
cyber	O
security	O
personnel	O
,	O
"	O
XXE	O
attack	O
when	O
performed	O
successfully	O
can	O
disclose	O
local	O
files	O
in	O
the	O
file	B-General_Concept
system	O
of	O
the	O
website	O
.	O
</s>
<s>
It	O
is	O
like	O
an	O
unsafe	O
guessable	O
password	O
;	O
XML	B-Protocol
documents	I-Protocol
give	O
precise	O
information	O
about	O
its	O
users	O
.	O
</s>
<s>
Simplified	O
Example	O
of	O
a	O
Schema	O
File	B-General_Concept
:	O
</s>
<s>
ZIP	B-General_Concept
bombs	O
are	O
malicious	O
archive	B-Application
file	I-Application
designed	O
to	O
crash	O
or	O
render	O
a	O
program	O
useless	O
.	O
</s>
<s>
One	O
example	O
of	O
a	O
zip	B-General_Concept
bomb	O
is	O
the	O
file	B-General_Concept
42.zip	O
,	O
which	O
is	O
a	O
file	B-General_Concept
consisting	O
of	O
42	O
kilobytes	O
of	O
compressed	O
data	O
,	O
containing	O
five	O
layers	O
of	O
each	O
bottom-layer	O
archive	B-Application
that	O
contains	O
4.3-gigabytes	O
.	O
</s>
<s>
Unlike	O
other	O
ways	O
of	O
high-jacking	O
a	O
system	O
,	O
zip	B-General_Concept
bombs	O
use	O
compressed	O
files	O
to	O
that	O
take	O
excessive	O
amount	O
of	O
disk	B-General_Concept
space	I-General_Concept
,	O
time	O
,	O
or	O
memory	O
once	O
unpacked/opened	O
.	O
</s>
<s>
Often	O
times	O
zip	B-General_Concept
bomb	O
attackers	O
target	O
unknowing	O
employees	O
from	O
start-ups	O
and	O
big	O
corporations	O
to	O
open	O
the	O
zip	B-General_Concept
files	I-General_Concept
through	O
an	O
email	O
.	O
</s>
<s>
The	O
attacker	O
then	O
uses	O
the	O
decompressed	O
archive	B-Application
file	I-Application
for	O
ransomed	O
to	O
disarm	O
the	O
file	B-General_Concept
.	O
</s>
<s>
DDoS	O
attacks	O
are	O
a	O
form	O
of	O
attack	O
orchestrated	O
by	O
multiple	O
networks	O
pinning	O
on	O
one	O
Web	B-Application
server	I-Application
to	O
create	O
a	O
denial-of-service	O
error	O
.	O
</s>
<s>
The	O
attack	O
targeted	O
Google	B-Application
services	O
and	O
reached	O
a	O
size	O
of	O
2.54	O
Tbps	O
.	O
</s>
<s>
Google	B-Application
Cloud	O
disclosed	O
the	O
attack	O
in	O
October	O
2020	O
.	O
</s>
<s>
Google	B-Application
was	O
able	O
to	O
stop	O
the	O
breach	O
attack	O
through	O
google	B-Application
cloud	O
server	O
algorithms	O
.	O
</s>
<s>
According	O
to	O
the	B-Application
Google	I-Application
Cloud	O
Blog	O
,	O
"	O
On	O
June	O
1	O
,	O
a	O
Google	B-Application
Cloud	O
Armor	O
customer	O
was	O
targeted	O
with	O
a	O
series	O
of	O
HTTPS	O
DDoS	O
attacks	O
which	O
peaked	O
at	O
46	O
million	O
requests	O
per	O
second	O
.	O
</s>
