<s>
Internet	B-Application
security	I-Application
is	O
a	O
branch	O
of	O
computer	O
security	O
.	O
</s>
<s>
It	O
encompasses	O
the	O
Internet	O
,	O
browser	B-Protocol
security	I-Protocol
,	O
web	O
site	O
security	O
,	O
and	O
network	B-General_Concept
security	O
as	O
it	O
applies	O
to	O
other	O
applications	B-Application
or	O
operating	B-General_Concept
systems	I-General_Concept
as	O
a	O
whole	O
.	O
</s>
<s>
A	O
botnet	B-Architecture
is	O
a	O
network	B-General_Concept
of	O
computers	O
that	O
have	O
been	O
taken	O
over	O
by	O
a	O
robot	O
or	O
bot	B-Protocol
that	O
performs	O
large-scale	O
malicious	O
acts	O
for	O
its	O
creator	O
.	O
</s>
<s>
Computer	O
worms	O
are	O
programs	O
that	O
can	O
replicate	O
themselves	O
throughout	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
Often	O
referred	O
to	O
as	O
keylogging	O
or	O
keyboard	B-Device
capturing	O
,	O
is	O
the	O
action	O
of	O
recording	O
(	O
logging	O
)	O
the	O
keys	O
struck	O
on	O
a	O
keyboard	B-Device
.	O
</s>
<s>
DoS	O
may	O
target	O
cloud	B-Architecture
computing	I-Architecture
systems	O
.	O
</s>
<s>
DoS	O
attacks	O
often	O
use	O
bots	B-Protocol
(	O
or	O
a	O
botnet	B-Architecture
)	O
to	O
carry	O
out	O
the	O
attack	O
.	O
</s>
<s>
Applications	B-Application
used	O
to	O
access	O
Internet	O
resources	O
may	O
contain	O
security	O
vulnerabilities	O
such	O
as	O
memory	B-Application
safety	I-Application
bugs	O
or	O
flawed	O
authentication	O
checks	O
.	O
</s>
<s>
Such	O
bugs	O
can	O
give	O
network	B-General_Concept
attackers	O
full	O
control	O
over	O
the	O
computer	O
.	O
</s>
<s>
A	O
widespread	O
web-browser	O
application	O
vulnerability	O
is	O
the	O
cross-origin	O
resource	O
sharing	O
(	O
CORS	O
)	O
vulnerability	O
-	O
for	O
maximum	O
security	O
and	O
privacy	O
,	O
make	O
sure	O
to	O
adopt	O
adequate	O
countermeasures	O
against	O
it	O
(	O
such	O
as	O
the	O
patches	O
provided	O
for	O
WebKit-based	O
browsers	O
)	O
.	O
</s>
<s>
TCP/IP	B-Protocol
protocols	I-Protocol
may	O
be	O
secured	O
with	O
cryptographic	O
methods	O
and	O
security	B-Protocol
protocols	I-Protocol
.	O
</s>
<s>
These	O
protocols	O
include	O
Secure	B-Protocol
Sockets	I-Protocol
Layer	I-Protocol
(	O
SSL	O
)	O
,	O
succeeded	O
by	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
for	O
web	O
traffic	O
,	O
Pretty	B-Application
Good	I-Application
Privacy	I-Application
(	O
PGP	O
)	O
for	O
email	O
,	O
and	O
IPsec	B-Protocol
for	O
network	B-General_Concept
layer	O
security	O
.	O
</s>
<s>
IPsec	B-Protocol
is	O
designed	O
to	O
protect	O
TCP/IP	B-Protocol
communication	O
in	O
a	O
secure	O
manner	O
.	O
</s>
<s>
Two	O
main	O
types	O
of	O
transformation	O
form	O
the	O
basis	O
of	O
IPsec	B-Protocol
:	O
the	O
Authentication	O
Header	O
(	O
AH	O
)	O
and	O
ESP	O
.	O
</s>
<s>
They	O
provide	O
data	O
integrity	O
,	O
data	B-Error_Name
origin	I-Error_Name
authentication	I-Error_Name
,	O
and	O
anti-replay	B-Protocol
services	O
.	O
</s>
<s>
The	O
IPsec	B-Protocol
implementation	O
is	O
operated	O
in	O
a	O
host	O
or	O
security	O
gateway	O
environment	O
giving	O
protection	O
to	O
IP	O
traffic	O
.	O
</s>
<s>
Using	O
a	O
network	B-General_Concept
connection	O
,	O
the	O
mail	O
client	O
sends	O
the	O
sender	O
's	O
identity	O
,	O
the	O
recipient	O
list	O
and	O
the	O
message	O
content	O
to	O
the	O
server	O
.	O
</s>
<s>
Pretty	B-Application
Good	I-Application
Privacy	I-Application
provides	O
confidentiality	O
by	O
encrypting	O
messages	O
to	O
be	O
transmitted	O
or	O
data	O
files	O
to	O
be	O
stored	O
using	O
an	O
encryption	O
algorithm	O
such	O
as	O
Triple	B-Algorithm
DES	I-Algorithm
or	O
CAST-128	B-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
the	O
organizations	O
could	O
establish	O
a	O
virtual	B-Application
private	I-Application
network	I-Application
(	O
VPN	B-Application
)	O
to	O
encrypt	O
communications	O
between	O
their	O
mail	O
servers	O
.	O
</s>
<s>
Unlike	O
methods	O
that	O
only	O
encrypt	O
a	O
message	O
body	O
,	O
a	O
VPN	B-Application
can	O
encrypt	O
all	O
communication	O
over	O
the	O
connection	O
,	O
including	O
email	O
header	O
information	O
such	O
as	O
senders	O
,	O
recipients	O
,	O
and	O
subjects	O
.	O
</s>
<s>
However	O
,	O
a	O
VPN	B-Application
does	O
not	O
provide	O
a	O
message	O
signing	O
mechanism	O
,	O
nor	O
can	O
it	O
provide	O
protection	O
for	O
email	O
messages	O
along	O
the	O
entire	O
route	O
from	O
sender	O
to	O
recipient	O
.	O
</s>
<s>
A	O
Message	B-Algorithm
authentication	I-Algorithm
code	I-Algorithm
(	O
MAC	O
)	O
is	O
a	O
cryptography	O
method	O
that	O
uses	O
a	O
secret	O
key	O
to	O
digitally	O
sign	O
a	O
message	O
.	O
</s>
<s>
The	O
Message	B-Algorithm
Authentication	I-Algorithm
Code	I-Algorithm
protects	O
both	O
a	O
message	O
's	O
data	O
integrity	O
as	O
well	O
as	O
its	O
authenticity	B-Error_Name
.	O
</s>
<s>
A	O
computer	B-Application
firewall	I-Application
controls	O
access	O
to	O
a	O
single	O
computer	O
.	O
</s>
<s>
A	O
network	B-Application
firewall	I-Application
controls	O
access	O
to	O
an	O
entire	O
network	B-General_Concept
.	O
</s>
<s>
A	O
firewall	B-Application
is	O
a	O
security	O
device	O
—	O
computer	O
hardware	O
or	O
software	O
—	O
that	O
filters	O
traffic	O
and	O
blocks	O
outsiders	O
.	O
</s>
<s>
Firewalls	B-Application
can	O
also	O
screen	O
network	B-General_Concept
traffic	O
and	O
block	O
traffic	O
deemed	O
unauthorized	O
.	O
</s>
<s>
Firewalls	B-Application
restrict	O
incoming	O
and	O
outgoing	O
network	B-Protocol
packets	I-Protocol
.	O
</s>
<s>
Firewalls	B-Application
create	O
checkpoints	O
between	O
networks	B-Architecture
and	O
computers	O
.	O
</s>
<s>
Firewalls	B-Application
can	O
block	O
traffic	O
based	O
on	O
IP	O
source	O
and	O
TCP	B-Protocol
port	I-Protocol
number	O
.	O
</s>
<s>
They	O
can	O
also	O
serve	O
as	O
the	O
platform	O
for	O
IPsec	B-Protocol
.	O
</s>
<s>
Using	O
tunnel	O
mode	O
,	O
firewalls	B-Application
can	O
implement	O
VPNs	B-Application
.	O
</s>
<s>
Firewalls	B-Application
can	O
also	O
limit	O
network	B-General_Concept
exposure	O
by	O
hiding	O
the	O
internal	O
network	B-General_Concept
from	O
the	O
public	O
Internet	O
.	O
</s>
<s>
A	O
packet	B-Protocol
filter	O
processes	O
network	B-General_Concept
traffic	O
on	O
a	O
packet-by-packet	O
basis	O
.	O
</s>
<s>
Its	O
main	O
job	O
is	O
to	O
filter	O
traffic	O
from	O
a	O
remote	O
IP	O
host	O
,	O
so	O
a	O
router	O
is	O
needed	O
to	O
connect	O
the	O
internal	O
network	B-General_Concept
to	O
the	O
Internet	O
.	O
</s>
<s>
The	O
router	O
is	O
known	O
as	O
a	O
screening	O
router	O
,	O
which	O
screens	O
packets	B-Protocol
leaving	O
and	O
entering	O
the	O
network	B-General_Concept
.	O
</s>
<s>
In	O
a	O
stateful	O
firewall	B-Application
the	O
circuit-level	B-Protocol
gateway	I-Protocol
is	O
a	O
proxy	B-Application
server	I-Application
that	O
operates	O
at	O
the	O
network	B-General_Concept
level	O
of	O
an	O
Open	O
Systems	O
Interconnect	O
(	O
OSI	O
)	O
model	O
and	O
statically	O
defines	O
what	O
traffic	O
will	O
be	O
allowed	O
.	O
</s>
<s>
Circuit	O
proxies	O
forward	O
network	B-Protocol
packets	I-Protocol
(	O
formatted	O
data	O
)	O
containing	O
a	O
given	O
port	B-Protocol
number	I-Protocol
,	O
if	O
the	O
port	B-Protocol
is	O
permitted	O
by	O
the	O
algorithm	O
.	O
</s>
<s>
The	O
main	O
advantage	O
of	O
a	O
proxy	B-Application
server	I-Application
is	O
its	O
ability	O
to	O
provide	O
Network	B-Protocol
Address	I-Protocol
Translation	I-Protocol
(	O
NAT	O
)	O
,	O
which	O
can	O
hide	O
the	O
user	O
's	O
IP	O
address	O
from	O
the	O
Internet	O
,	O
effectively	O
protecting	O
internal	O
information	O
from	O
the	O
outside	O
.	O
</s>
<s>
An	O
application-level	B-Protocol
firewall	I-Protocol
is	O
a	O
third-generation	O
firewall	B-Application
where	O
a	O
proxy	B-Application
server	I-Application
operates	O
at	O
the	O
very	O
top	O
of	O
the	O
OSI	O
model	O
,	O
the	O
IP	B-Protocol
suite	I-Protocol
application	O
level	O
.	O
</s>
<s>
A	O
network	B-Protocol
packet	I-Protocol
is	O
forwarded	O
only	O
if	O
a	O
connection	O
is	O
established	O
using	O
a	O
known	O
protocol	O
.	O
</s>
<s>
Application-level	O
gateways	O
are	O
notable	O
for	O
analyzing	O
entire	O
messages	O
rather	O
than	O
individual	O
packets	B-Protocol
.	O
</s>
<s>
For	O
example	O
,	O
Internet	B-Application
Explorer	I-Application
6	O
,	O
which	O
used	O
to	O
lead	O
the	O
market	O
,	O
was	O
heavily	O
attacked	O
.	O
</s>
<s>
Antivirus	B-Application
software	I-Application
can	O
protect	O
a	O
programmable	O
device	O
by	O
detecting	O
and	O
eliminating	O
malware	O
.	O
</s>
<s>
A	O
password	O
manager	O
is	O
a	O
software	B-Application
application	I-Application
that	O
creates	O
,	O
stores	O
and	O
provides	O
passwords	O
to	O
applications	B-Application
.	O
</s>
<s>
Security	O
suites	O
were	O
first	O
offered	O
for	O
sale	O
in	O
2003	O
(	O
McAfee	O
)	O
and	O
contain	O
firewalls	B-Application
,	O
anti-virus	B-Application
,	O
anti-spyware	O
and	O
other	O
components	O
.	O
</s>
<s>
Atalla	O
later	O
added	O
its	O
Identikey	O
hardware	O
security	O
module	O
,	O
andj	O
supported	O
processing	B-General_Concept
online	O
transactions	O
and	O
network	B-General_Concept
security	O
.	O
</s>
<s>
It	O
was	O
compatible	O
with	O
various	O
switching	B-Protocol
networks	B-Architecture
,	O
and	O
was	O
capable	O
of	O
resetting	O
itself	O
electronically	O
to	O
any	O
one	O
of	O
64,000	O
irreversible	O
nonlinear	O
algorithms	O
as	O
directed	O
by	O
card	O
data	O
information	O
.	O
</s>
<s>
In	O
1979	O
,	O
Atalla	O
introduced	O
the	O
first	O
network	B-General_Concept
security	O
processor	O
(	O
NSP	O
)	O
.	O
</s>
