<s>
Zeek	B-Application
is	O
a	O
free	B-License
and	I-License
open-source	I-License
software	I-License
network	O
analysis	O
framework	O
.	O
</s>
<s>
Vern	O
Paxson	O
began	O
development	O
work	O
on	O
Zeek	B-Application
in	O
1995	O
at	O
Lawrence	O
Berkeley	O
National	O
Lab	O
.	O
</s>
<s>
Zeek	B-Application
is	O
a	O
network	O
security	O
monitor	O
(	O
NSM	O
)	O
but	O
can	O
also	O
be	O
used	O
as	O
a	O
network	O
intrusion	O
detection	O
system	O
(	O
NIDS	O
)	O
.	O
</s>
<s>
The	O
Zeek	B-Application
project	O
releases	O
the	O
software	O
under	O
the	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Zeek	B-Application
's	O
purpose	O
is	O
to	O
inspect	O
network	O
traffic	O
and	O
generate	O
a	O
variety	O
of	O
logs	O
describing	O
the	O
activity	O
it	O
sees	O
.	O
</s>
<s>
The	O
following	O
is	O
an	O
example	O
of	O
one	O
entry	O
in	O
JSON	B-General_Concept
format	O
from	O
the	O
conn.log	O
:	O
</s>
<s>
One	O
of	O
Zeek	B-Application
's	O
primary	O
use	O
cases	O
involves	O
cyber	O
threat	O
hunting	O
.	O
</s>
<s>
Dr.	O
Paxson	O
originally	O
named	O
the	O
software	O
"	O
Bro	B-Application
"	O
as	O
a	O
warning	O
regarding	O
George	O
Orwell	O
's	O
Big	O
Brother	O
from	O
the	O
novel	O
Nineteen	O
Eighty-Four	O
.	O
</s>
<s>
At	O
LBNL	O
in	O
the	O
1990s	O
,	O
the	O
developers	O
ran	O
their	O
sensors	O
as	O
a	O
pseudo-user	O
named	O
“	O
zeek	B-Application
”	O
,	O
thereby	O
inspiring	O
the	O
name	O
change	O
in	O
2018	O
.	O
</s>
<s>
They	O
deploy	O
one	O
or	O
more	O
network	B-Device
taps	I-Device
or	O
enable	O
switch	O
SPAN	B-Protocol
ports	I-Protocol
for	O
port	B-Protocol
mirroring	I-Protocol
to	O
gain	O
access	O
to	O
traffic	O
.	O
</s>
<s>
They	O
deploy	O
Zeek	B-Application
on	O
servers	O
with	O
access	O
to	O
those	O
visibility	O
points	O
.	O
</s>
<s>
The	O
Zeek	B-Application
software	O
on	O
the	O
server	O
deciphers	O
network	O
traffic	O
as	O
logs	O
,	O
writing	O
them	O
to	O
local	O
disk	O
or	O
remote	O
storage	O
.	O
</s>
<s>
Zeek	B-Application
's	O
event	O
engine	O
analyzes	O
live	O
or	O
recorded	O
network	O
traffic	O
to	O
generate	O
neutral	O
event	O
logs	O
.	O
</s>
<s>
Zeek	B-Application
uses	O
common	O
ports	O
and	O
dynamic	O
protocol	O
detection	O
(	O
involving	O
signatures	O
as	O
well	O
as	O
behavioral	O
analysis	O
)	O
to	O
identify	O
network	O
protocols	O
.	O
</s>
<s>
Developers	O
write	O
Zeek	B-Application
policy	O
scripts	O
in	O
the	O
Turing	B-Algorithm
complete	I-Algorithm
Zeek	B-Application
scripting	O
language	O
.	O
</s>
<s>
By	O
default	O
Zeek	B-Application
logs	O
information	O
about	O
events	O
to	O
files	O
,	O
but	O
analysts	O
can	O
also	O
configure	O
Zeek	B-Application
to	O
take	O
other	O
actions	O
,	O
such	O
as	O
sending	O
an	O
email	O
,	O
raising	O
an	O
alert	O
,	O
executing	O
a	O
system	O
command	O
,	O
updating	O
an	O
internal	O
metric	O
,	O
or	O
calling	O
another	O
Zeek	B-Application
script	O
.	O
</s>
<s>
Zeek	B-Application
analyzers	O
perform	O
application	O
layer	O
decoding	O
,	O
anomaly	O
detection	O
,	O
signature	O
matching	O
and	O
connection	O
analysis	O
.	O
</s>
<s>
Zeek	B-Application
's	O
developers	O
designed	O
the	O
software	O
to	O
incorporate	O
additional	O
analyzers	O
.	O
</s>
