<s>
Cisco	B-Application
NAC	I-Application
Appliance	I-Application
,	O
formerly	O
Cisco	B-Application
Clean	I-Application
Access	I-Application
(	O
CCA	O
)	O
,	O
was	O
a	O
network	O
admission	O
control	O
(	O
NAC	O
)	O
system	O
developed	O
by	O
Cisco	O
Systems	O
designed	O
to	O
produce	O
a	O
secure	O
and	O
clean	O
computer	O
network	O
environment	O
.	O
</s>
<s>
The	O
system	O
usually	O
installs	O
an	O
application	O
known	O
as	O
the	O
Clean	B-Application
Access	I-Application
Agent	I-Application
on	O
computers	O
that	O
will	O
be	O
connected	O
to	O
the	O
network	O
.	O
</s>
<s>
This	O
application	O
,	O
in	O
conjunction	O
with	O
both	O
a	O
Clean	B-Application
Access	I-Application
server	O
and	O
a	O
Clean	B-Application
Access	I-Application
Manager	O
,	O
has	O
become	O
common	O
in	O
many	O
universities	O
and	O
corporate	O
environments	O
today	O
.	O
</s>
<s>
It	O
is	O
capable	O
of	O
managing	O
wired	O
or	O
wireless	O
networks	O
in	O
an	O
in-band	O
or	O
out-of-band	B-Protocol
configuration	O
mode	O
,	O
and	O
Virtual	B-Application
Private	I-Application
networks	I-Application
(	O
VPN	B-Application
)	O
in	O
an	O
in-band	O
only	O
configuration	O
mode	O
.	O
</s>
<s>
Cisco	B-Application
NAC	I-Application
Appliance	I-Application
is	O
no	O
longer	O
in	O
production	O
and	O
no	O
longer	O
sold	O
as	O
of	O
the	O
early	O
2010s	O
.	O
</s>
<s>
The	O
Clean	B-Application
Access	I-Application
Agent	I-Application
(	O
abbreviation	O
:	O
CCAA	O
,	O
"	O
Cisco	B-Application
Clean	I-Application
Access	I-Application
Agent	I-Application
"	O
)	O
resides	O
on	O
the	O
client	O
's	O
machine	O
,	O
authenticates	O
the	O
user	O
,	O
and	O
scans	O
for	O
the	O
required	O
patches	O
and	O
software	O
.	O
</s>
<s>
Currently	O
the	O
Clean	B-Application
Access	I-Application
Agent	I-Application
application	O
is	O
only	O
available	O
for	O
some	O
Windows	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
operating	B-General_Concept
systems	I-General_Concept
(	O
Windows	B-Device
98	I-Device
,	O
Windows	B-Device
Me	I-Device
,	O
Windows	B-Application
2000	I-Application
,	O
Windows	B-Application
XP	I-Application
,	O
Windows	B-Application
XP	I-Application
Media	I-Application
Center	I-Application
Edition	I-Application
,	O
Windows	B-Application
Vista	I-Application
,	O
Windows	B-Device
7	I-Device
,	O
Windows	B-Application
8	I-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
)	O
;	O
most	O
network	O
administrators	O
allow	O
clients	O
with	O
non-Windows	O
operating	B-General_Concept
systems	I-General_Concept
(	O
such	O
as	O
Mac	B-Operating_System
OS	I-Operating_System
9	I-Operating_System
,	O
Linux	B-Application
,	O
and	O
FreeBSD	B-Operating_System
)	O
to	O
access	O
the	O
network	O
without	O
any	O
security	O
checks	O
(	O
authentication	O
is	O
still	O
required	O
and	O
is	O
usually	O
handled	O
via	O
a	O
Web	O
interface	O
)	O
.	O
</s>
<s>
After	O
successfully	O
authenticating	O
via	O
a	O
web	O
interface	O
,	O
the	O
Clean	B-Application
Access	I-Application
Server	O
will	O
direct	O
new	O
Windows	B-Application
based	O
clients	O
to	O
download	O
and	O
install	O
the	O
Clean	B-Application
Access	I-Application
Agent	I-Application
application	O
(	O
at	O
this	O
time	O
,	O
non-Windows	O
based	O
clients	O
need	O
only	O
authenticate	O
via	O
the	O
web	O
interface	O
and	O
agree	O
to	O
any	O
network	O
terms	O
of	O
service	O
)	O
.	O
</s>
<s>
Once	O
re-authenticated	O
,	O
the	O
Agent	O
software	O
will	O
typically	O
check	O
the	O
client	O
computer	O
for	O
known	O
vulnerabilities	O
to	O
the	O
Windows	B-Application
operating	I-Application
system	I-Application
being	O
used	O
,	O
as	O
well	O
as	O
for	O
updated	O
anti-virus	O
software	O
and	O
definitions	O
.	O
</s>
<s>
The	O
checks	O
are	O
maintained	O
as	O
a	O
series	O
of	O
"	O
rules	O
"	O
on	O
the	O
Clean	B-Application
Access	I-Application
Manager	O
side	O
.	O
</s>
<s>
The	O
Clean	B-Application
Access	I-Application
Manager	O
(	O
CAM	O
)	O
can	O
be	O
configured	O
to	O
check	O
,	O
install	O
,	O
or	O
update	O
anything	O
on	O
the	O
user	O
's	O
system	O
.	O
</s>
<s>
Failed	O
messages	O
inform	O
the	O
user	O
of	O
what	O
category(s )	O
the	O
system	O
failed	O
(	O
Windows	B-Application
updates	O
,	O
antivirus	O
,	O
etc	O
.	O
</s>
<s>
Any	O
system	O
failing	O
the	O
checks	O
will	O
be	O
denied	O
general	O
access	O
to	O
the	O
network	O
and	O
will	O
probably	O
be	O
placed	O
in	O
a	O
quarantined	O
role	O
(	O
how	O
exactly	O
a	O
failed	O
system	O
is	O
handled	O
depends	O
entirely	O
on	O
how	O
the	O
Clean	B-Application
Access	I-Application
Manager	O
is	O
configured	O
,	O
and	O
may	O
vary	O
from	O
network	O
to	O
network	O
.	O
</s>
<s>
In	O
such	O
a	O
case	O
,	O
the	O
user	O
is	O
only	O
allowed	O
connectivity	O
to	O
the	O
Windows	B-Application
Update	O
website	O
and	O
a	O
number	O
of	O
antivirus	O
providers	O
(	O
Symantec	O
,	O
McAfee	O
,	O
Trend	O
Micro	O
,	O
etc	O
.	O
</s>
<s>
The	O
user	O
has	O
the	O
option	O
of	O
re-authenticating	O
with	O
Clean	B-Application
Access	I-Application
again	O
,	O
and	O
continuing	O
the	O
process	O
as	O
needed	O
.	O
</s>
<s>
Systems	O
passing	O
the	O
checks	O
are	O
granted	O
access	O
to	O
the	O
network	O
as	O
defined	O
by	O
the	O
assigned	O
role	O
on	O
the	O
Clean	B-Application
Access	I-Application
Manager	O
.	O
</s>
<s>
Clean	B-Application
Access	I-Application
configurations	O
vary	O
from	O
site	O
to	O
site	O
.	O
</s>
<s>
The	O
network	O
services	O
available	O
will	O
also	O
vary	O
based	O
on	O
Clean	B-Application
Access	I-Application
configuration	O
and	O
the	O
assigned	O
user	O
role	O
.	O
</s>
<s>
Clean	B-Application
Access	I-Application
normally	O
checks	O
a	O
Windows	B-Application
system	O
for	O
required	O
updates	O
by	O
checking	O
the	O
system	O
's	O
registry	B-Protocol
.	O
</s>
<s>
A	O
corrupted	O
registry	B-Protocol
may	O
keep	O
a	O
user	O
from	O
being	O
able	O
to	O
access	O
the	O
network	O
.	O
</s>
<s>
The	O
Clean	B-Application
Access	I-Application
Server	O
(	O
CAS	O
)	O
determines	O
the	O
client	O
's	O
operating	B-General_Concept
system	I-General_Concept
by	O
reading	O
the	O
browser	O
's	O
user	B-Protocol
agent	I-Protocol
string	O
after	O
authentication	O
.	O
</s>
<s>
If	O
a	O
Windows	B-Application
system	O
is	O
detected	O
,	O
then	O
the	O
server	O
will	O
ask	O
the	O
user	O
to	O
download	O
the	O
Clean	B-Application
Access	I-Application
Agent	I-Application
;	O
on	O
all	O
other	O
operating	B-General_Concept
systems	I-General_Concept
,	O
login	O
is	O
complete	O
.	O
</s>
<s>
To	O
combat	O
attempts	O
to	O
spoof	O
the	O
OS	O
in	O
use	O
on	O
the	O
client	O
,	O
newer	O
versions	O
of	O
the	O
Server	O
and	O
Agent	O
(	O
3.6.0	O
and	O
up	O
)	O
also	O
probe	O
the	O
host	O
via	O
TCP/IP	B-Protocol
stack	I-Protocol
fingerprinting	I-Protocol
and	O
JavaScript	B-Language
to	O
verify	O
the	O
machine	O
's	O
operating	B-General_Concept
system	I-General_Concept
:	O
</s>
<s>
By	O
default	O
,	O
the	O
system	O
uses	O
the	O
User-Agent	B-Protocol
string	O
from	O
the	O
HTTP	B-Protocol
header	O
to	O
determine	O
the	O
client	O
OS	O
.	O
</s>
<s>
Release	O
3.6.0	O
provides	O
additional	O
detection	O
options	O
to	O
include	O
using	O
the	O
platform	O
information	O
from	O
JavaScript	B-Language
or	O
OS	B-Protocol
fingerprinting	I-Protocol
from	O
the	O
TCP/IP	B-Protocol
handshake	O
to	O
determine	O
the	O
client	O
OS	O
.	O
</s>
<s>
This	O
feature	O
is	O
intended	O
to	O
prevent	O
users	O
from	O
changing	O
identification	O
of	O
their	O
client	O
operating	B-General_Concept
systems	I-General_Concept
through	O
manipulating	O
HTTP	B-Protocol
information	O
.	O
</s>
<s>
Note	O
that	O
this	O
is	O
a	O
"	O
passive	O
"	O
detection	O
technique	O
that	O
only	O
inspects	O
the	O
TCP	O
handshake	O
and	O
is	O
not	O
impacted	O
by	O
the	O
presence	O
of	O
a	O
firewall	B-Application
.	O
</s>
<s>
The	O
Clean	B-Application
Access	I-Application
Agent	I-Application
makes	O
extensive	O
use	O
of	O
the	O
Windows	B-Language
Script	I-Language
Engine	I-Language
,	O
version	O
5.6	O
.	O
</s>
<s>
It	O
was	O
demonstrated	O
that	O
removal	O
or	O
disabling	O
of	O
the	O
scripting	O
engine	O
in	O
MS	B-Application
Windows	I-Application
will	O
bypass	O
and	O
break	O
posture	O
interrogation	O
by	O
the	O
Clean	B-Application
Access	I-Application
Agent	I-Application
,	O
which	O
will	O
"	O
fail	O
open	O
"	O
and	O
allow	O
devices	O
to	O
connect	O
to	O
a	O
network	O
upon	O
proper	O
authentication	O
.	O
</s>
<s>
While	O
MAC	O
address	O
spoofing	O
may	O
be	O
accomplished	O
in	O
a	O
wireless	O
environment	O
by	O
means	O
of	O
using	O
a	O
sniffer	B-Protocol
to	O
detect	O
and	O
clone	O
the	O
MAC	O
address	O
of	O
a	O
client	O
who	O
has	O
already	O
been	O
authorized	O
or	O
placed	O
in	O
a	O
"	O
clean	O
"	O
user	O
role	O
,	O
it	O
is	O
not	O
easy	O
to	O
do	O
so	O
in	O
a	O
wired	O
environment	O
,	O
unless	O
the	O
Clean	B-Application
Access	I-Application
Server	O
has	O
been	O
misconfigured	O
.	O
</s>
<s>
In	O
a	O
correct	O
architecture	O
and	O
configuration	O
,	O
the	O
Clean	B-Application
Access	I-Application
Server	O
would	O
hand	O
out	O
IP	B-Protocol
subnets	I-Protocol
and	O
addresses	O
via	O
DHCP	B-Protocol
on	O
its	O
untrusted	O
interface	O
using	O
a	O
30-bit	O
network	O
address	O
and	O
2	O
bits	O
for	O
hosts	O
,	O
therefore	O
only	O
one	O
host	O
could	O
be	O
placed	O
in	O
each	O
DHCP	B-Protocol
scope/subnet	O
at	O
any	O
given	O
time	O
.	O
</s>
<s>
Proper	O
and	O
similar	O
implementation	O
in	O
a	O
wireless	O
environment	O
would	O
in	O
fact	O
contribute	O
to	O
a	O
more	O
secure	O
instance	O
of	O
Clean	B-Application
Access	I-Application
.	O
</s>
<s>
Timers	O
allow	O
administrators	O
to	O
clear	O
the	O
list	O
of	O
certified	O
MAC	O
addresses	O
on	O
a	O
regular	O
basis	O
and	O
force	O
a	O
re-authorization	O
of	O
devices	O
and	O
users	O
to	O
the	O
Clean	B-Application
Access	I-Application
Server	O
.	O
</s>
<s>
Cisco	B-Application
NAC	I-Application
Appliance	I-Application
is	O
notorious	O
for	O
creating	O
disruptions	O
in	O
the	O
Internet	O
connections	O
of	O
users	O
,	O
considering	O
a	O
continuous	O
connection	O
between	O
a	O
computer	O
and	O
a	O
server	O
or	O
another	O
computer	O
as	O
suspicious	O
activity	O
.	O
</s>
<s>
This	O
is	O
problematic	O
for	O
individuals	O
using	O
Skype	B-Application
or	O
any	O
webcam	O
activity	O
as	O
well	O
as	O
online	O
games	O
such	O
as	O
World	B-Protocol
of	I-Protocol
Warcraft	I-Protocol
.	O
</s>
<s>
With	O
online	O
games	O
,	O
the	O
disruptions	O
created	O
by	O
Cisco	B-Application
NAC	I-Application
Appliance	I-Application
cause	O
the	O
player	O
to	O
be	O
logged	O
off	O
the	O
gaming	O
server	O
.	O
</s>
