<s>
Search	B-Application
engine	I-Application
scraping	I-Application
is	O
the	O
process	O
of	O
harvesting	O
URLs	O
,	O
descriptions	O
,	O
or	O
other	O
information	O
from	O
search	B-Application
engines	I-Application
such	O
as	O
Google	B-Application
,	O
Bing	B-Application
,	O
Yahoo	B-Application
,	O
or	O
Yandex	O
.	O
</s>
<s>
This	O
is	O
a	O
specific	O
form	O
of	O
screen	O
scraping	O
or	O
web	B-Application
scraping	I-Application
dedicated	O
to	O
search	B-Application
engines	I-Application
only	O
.	O
</s>
<s>
Most	O
commonly	O
larger	O
search	B-Application
engine	I-Application
optimization	O
(	O
SEO	O
)	O
providers	O
depend	O
on	O
regularly	O
scraping	O
keywords	O
from	O
search	B-Application
engines	I-Application
,	O
especially	O
Google	B-Application
,	O
Sogou	O
to	O
monitor	O
the	O
competitive	O
position	O
of	O
their	O
customers	O
 '	O
websites	O
for	O
relevant	O
keywords	O
or	O
their	O
indexing	B-Application
status	O
.	O
</s>
<s>
Search	B-Application
engines	I-Application
like	O
Google	B-Application
have	O
implemented	O
various	O
forms	O
of	O
human	O
detection	O
to	O
block	O
any	O
sort	O
of	O
automated	O
access	O
to	O
their	O
service	O
,	O
in	O
the	O
intent	O
of	O
driving	O
the	O
users	O
of	O
scrapers	O
towards	O
buying	O
their	O
official	O
APIs	B-General_Concept
instead	O
.	O
</s>
<s>
The	O
process	O
of	O
entering	O
a	O
website	O
and	O
extracting	O
data	O
in	O
an	O
automated	O
fashion	O
is	O
also	O
often	O
called	O
"	O
crawling	B-Application
"	O
.	O
</s>
<s>
Search	B-Application
engine	I-Application
’s	O
like	O
Google	B-Application
,	O
Bing	B-Application
,	O
Yahoo	B-Application
or	O
Sogou	O
get	O
almost	O
all	O
their	O
data	O
from	O
automated	O
crawling	B-Application
bots	O
.	O
</s>
<s>
Search	B-Application
engines	I-Application
are	O
an	O
integral	O
part	O
of	O
the	O
modern	O
online	O
ecosystem	O
.	O
</s>
<s>
In	O
fact	O
,	O
more	O
than	O
90%	O
of	O
online	O
experiences	O
begin	O
with	O
a	O
search	B-Application
engine	I-Application
,	O
and	O
the	O
top	O
search	B-Application
results	I-Application
receive	O
the	O
majority	O
of	O
clicks	O
.	O
</s>
<s>
SEO	O
is	O
essential	O
because	O
it	O
enables	O
websites	O
to	O
rank	O
higher	O
in	O
search	B-Application
results	I-Application
pages	O
,	O
making	O
it	O
easier	O
for	O
people	O
to	O
find	O
them	O
.	O
</s>
<s>
A	O
higher	O
ranking	O
in	O
search	B-Application
results	I-Application
can	O
increase	O
a	O
website	O
's	O
visibility	O
,	O
traffic	O
,	O
and	O
ultimately	O
,	O
revenue	O
.	O
</s>
<s>
Google	B-Application
is	O
the	O
by	O
far	O
the	O
largest	O
search	B-Application
engine	I-Application
with	O
most	O
users	O
in	O
numbers	O
as	O
well	O
as	O
most	O
revenue	O
in	O
creative	O
advertisements	O
,	O
which	O
makes	O
Google	B-Application
the	O
most	O
important	O
search	B-Application
engine	I-Application
to	O
scrape	O
for	O
SEO	O
related	O
companies	O
.	O
</s>
<s>
Although	O
Google	B-Application
does	O
not	O
take	O
legal	O
action	O
against	O
scraping	O
,	O
it	O
uses	O
a	O
range	O
of	O
defensive	O
methods	O
that	O
makes	O
scraping	O
their	O
results	O
a	O
challenging	O
task	O
,	O
even	O
when	O
the	O
scraping	O
tool	O
is	O
realistically	O
spoofing	O
a	O
normal	O
web	O
browser	O
:	O
</s>
<s>
Google	B-Application
is	O
using	O
a	O
complex	O
system	O
of	O
request	O
rate	O
limitation	O
which	O
can	O
vary	O
for	O
each	O
language	O
,	O
country	O
,	O
User-Agent	O
as	O
well	O
as	O
depending	O
on	O
the	O
keywords	O
or	O
search	O
parameters	O
.	O
</s>
<s>
The	O
rate	O
limitation	O
can	O
make	O
it	O
unpredictable	O
when	O
accessing	O
a	O
search	B-Application
engine	I-Application
automated	O
,	O
as	O
the	O
behaviour	O
patterns	O
are	O
not	O
known	O
to	O
the	O
outside	O
developer	O
or	O
user	O
.	O
</s>
<s>
Network	O
and	O
IP	B-Protocol
limitations	O
are	O
as	O
well	O
part	O
of	O
the	O
scraping	O
defense	O
systems	O
.	O
</s>
<s>
Search	B-Application
engines	I-Application
can	O
not	O
easily	O
be	O
tricked	O
by	O
changing	O
to	O
another	O
IP	B-Protocol
,	O
while	O
using	O
proxies	O
is	O
a	O
very	O
important	O
part	O
in	O
successful	O
scraping	O
.	O
</s>
<s>
The	O
diversity	O
and	O
abusive	O
history	O
of	O
an	O
IP	B-Protocol
is	O
important	O
as	O
well	O
.	O
</s>
<s>
Offending	O
IPs	O
and	O
offending	O
IP	B-Protocol
networks	O
can	O
easily	O
be	O
stored	O
in	O
a	O
blacklist	O
database	O
to	O
detect	O
offenders	O
much	O
faster	O
.	O
</s>
<s>
The	O
fact	O
that	O
most	O
ISPs	O
give	O
dynamic	O
IP	B-Protocol
addresses	I-Protocol
to	O
customers	O
requires	O
that	O
such	O
automated	O
bans	O
be	O
only	O
temporary	O
,	O
do	O
not	O
block	O
innocent	O
users	O
.	O
</s>
<s>
Search	B-Application
engines	I-Application
serve	O
their	O
pages	O
to	O
millions	O
of	O
users	O
every	O
day	O
,	O
this	O
provides	O
a	O
large	O
amount	O
of	O
behaviour	O
information	O
.	O
</s>
<s>
Google	B-Application
for	O
example	O
has	O
a	O
very	O
sophisticated	O
behaviour	O
analyzation	O
system	O
,	O
possibly	O
using	O
deep	B-Algorithm
learning	I-Algorithm
software	O
to	O
detect	O
unusual	O
patterns	O
of	O
access	O
.	O
</s>
<s>
It	O
can	O
detect	O
unusual	O
activity	O
much	O
faster	O
than	O
other	O
search	B-Application
engines	I-Application
.	O
</s>
<s>
HTML	B-Language
markup	O
changes	O
,	O
depending	O
on	O
the	O
methods	O
used	O
to	O
harvest	O
the	O
content	O
of	O
a	O
website	O
,	O
even	O
a	O
small	O
change	O
in	O
HTML	B-Language
data	O
can	O
render	O
a	O
scraping	O
tool	O
broken	O
until	O
it	O
is	O
updated	O
.	O
</s>
<s>
In	O
the	O
past	O
years	O
search	B-Application
engines	I-Application
have	O
tightened	O
their	O
detection	O
systems	O
nearly	O
month	O
by	O
month	O
making	O
it	O
more	O
and	O
more	O
difficult	O
to	O
reliable	O
scrape	O
as	O
the	O
developers	O
need	O
to	O
experiment	O
and	O
adapt	O
their	O
code	O
regularly	O
.	O
</s>
<s>
When	O
search	B-Application
engine	I-Application
defense	O
thinks	O
an	O
access	O
might	O
be	O
automated	O
,	O
the	O
search	B-Application
engine	I-Application
can	O
react	O
differently	O
.	O
</s>
<s>
Solving	O
the	O
captcha	O
will	O
create	O
a	O
cookie	B-Application
that	O
permits	O
access	O
to	O
the	O
search	B-Application
engine	I-Application
again	O
for	O
a	O
while	O
.	O
</s>
<s>
The	O
second	O
layer	O
of	O
defense	O
is	O
a	O
similar	O
error	O
page	O
but	O
without	O
captcha	O
,	O
in	O
such	O
a	O
case	O
the	O
user	O
is	O
completely	O
blocked	O
from	O
using	O
the	O
search	B-Application
engine	I-Application
until	O
the	O
temporary	O
block	O
is	O
lifted	O
,	O
or	O
the	O
user	O
changes	O
their	O
IP	B-Protocol
.	O
</s>
<s>
Google	B-Application
has	O
blocked	O
large	O
network	O
blocks	O
for	O
months	O
.	O
</s>
<s>
All	O
these	O
forms	O
of	O
detection	O
may	O
also	O
happen	O
to	O
a	O
normal	O
user	O
,	O
especially	O
users	O
sharing	O
the	O
same	O
IP	B-Protocol
address	I-Protocol
or	O
network	O
class	O
(	O
IPV4	O
ranges	O
as	O
well	O
as	O
IPv6	O
ranges	O
)	O
.	O
</s>
<s>
To	O
scrape	O
a	O
search	B-Application
engine	I-Application
successfully	O
,	O
the	O
two	O
major	O
factors	O
are	O
time	O
and	O
amount	O
.	O
</s>
<s>
Proper	O
time	O
management	O
,	O
time	O
between	O
keyword	O
changes	O
,	O
pagination	O
as	O
well	O
as	O
correctly	O
placed	O
delays	O
Effective	O
longterm	O
scraping	O
rates	O
can	O
vary	O
from	O
only	O
3	O
–	O
5	O
requests	O
(	O
keywords	O
or	O
pages	O
)	O
per	O
hour	O
up	O
to	O
100	O
and	O
more	O
per	O
hour	O
for	O
each	O
IP	B-Protocol
address	I-Protocol
/	O
Proxy	O
in	O
use	O
.	O
</s>
<s>
This	O
framework	O
controls	O
browsers	O
over	O
the	O
DevTools	O
Protocol	O
and	O
makes	O
it	O
hard	O
for	O
Google	B-Application
to	O
detect	O
that	O
the	O
browser	O
is	O
automated	O
.	O
</s>
<s>
When	O
developing	O
a	O
scraper	O
for	O
a	O
search	B-Application
engine	I-Application
,	O
almost	O
any	O
programming	O
language	O
can	O
be	O
used	O
.	O
</s>
<s>
PHP	B-Application
is	O
a	O
commonly	O
used	O
language	O
to	O
write	O
scraping	O
scripts	O
for	O
websites	O
or	O
backend	O
services	O
,	O
since	O
it	O
has	O
powerful	O
capabilities	O
built-in	O
(	O
DOM	B-General_Concept
parsers	O
,	O
libcURL	O
)	O
;	O
however	O
,	O
its	O
memory	O
usage	O
is	O
typically	O
10	O
times	O
the	O
factor	O
of	O
a	O
similar	O
C/C	O
++	O
code	O
.	O
</s>
<s>
Ruby	B-Application
on	I-Application
Rails	I-Application
as	O
well	O
as	O
Python	B-Language
are	O
also	O
frequently	O
used	O
to	O
automated	O
scraping	O
jobs	O
.	O
</s>
<s>
For	O
highest	O
performance	O
,	O
C++	B-Language
DOM	B-General_Concept
parsers	O
should	O
be	O
considered	O
.	O
</s>
<s>
Additionally	O
,	O
bash	B-Operating_System
scripting	I-Operating_System
can	O
be	O
used	O
together	O
with	O
cURL	B-Language
as	O
a	O
command	O
line	O
tool	O
to	O
scrape	O
a	O
search	B-Application
engine	I-Application
.	O
</s>
<s>
When	O
developing	O
a	O
search	B-Application
engine	I-Application
scraper	O
there	O
are	O
several	O
existing	O
tools	O
and	O
libraries	O
available	O
that	O
can	O
either	O
be	O
used	O
,	O
extended	O
or	O
just	O
analyzed	O
to	O
learn	O
from	O
.	O
</s>
<s>
cURL	B-Language
–	O
a	O
command	O
line	O
browser	O
for	O
automation	O
and	O
testing	O
,	O
as	O
well	O
as	O
a	O
powerful	O
open	O
source	O
HTTP	O
interaction	O
library	O
available	O
for	O
a	O
large	O
range	O
of	O
programming	O
languages	O
.	O
</s>
<s>
Google-search	O
-	O
A	O
Go	O
package	O
to	O
scrape	O
Google	B-Application
.	O
</s>
<s>
Scrape	O
search	B-Application
engines	I-Application
concurrently	O
with	O
different	O
proxies	O
.	O
</s>
<s>
When	O
scraping	O
websites	O
and	O
services	O
the	O
legal	O
part	O
is	O
often	O
a	O
big	O
concern	O
for	O
companies	O
,	O
for	O
web	B-Application
scraping	I-Application
it	O
greatly	O
depends	O
on	O
the	O
country	O
a	O
scraping	O
user/company	O
is	O
from	O
as	O
well	O
as	O
which	O
data	O
or	O
website	O
is	O
being	O
scraped	O
.	O
</s>
<s>
However	O
,	O
when	O
it	O
comes	O
to	O
scraping	O
search	B-Application
engines	I-Application
the	O
situation	O
is	O
different	O
,	O
search	B-Application
engines	I-Application
usually	O
do	O
not	O
list	O
intellectual	O
property	O
as	O
they	O
just	O
repeat	O
or	O
summarize	O
information	O
they	O
scraped	O
from	O
other	O
websites	O
.	O
</s>
<s>
The	O
largest	O
public	O
known	O
incident	O
of	O
a	O
search	B-Application
engine	I-Application
being	O
scraped	O
happened	O
in	O
2011	O
when	O
Microsoft	O
was	O
caught	O
scraping	O
unknown	O
keywords	O
from	O
Google	B-Application
for	O
their	O
own	O
,	O
rather	O
new	O
Bing	B-Application
service	O
,	O
but	O
even	O
this	O
incident	O
did	O
not	O
result	O
in	O
a	O
court	O
case	O
.	O
</s>
<s>
One	O
possible	O
reason	O
might	O
be	O
that	O
search	B-Application
engines	I-Application
like	O
Google	B-Application
,	O
Sogou	O
are	O
getting	O
almost	O
all	O
their	O
data	O
by	O
scraping	O
millions	O
of	O
public	O
reachable	O
websites	O
,	O
also	O
without	O
reading	O
and	O
accepting	O
those	O
terms	O
.	O
</s>
