<s>
Fail2ban	B-Protocol
is	O
an	O
intrusion	O
prevention	O
software	O
framework	O
.	O
</s>
<s>
Written	O
in	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
,	O
it	O
is	O
designed	O
to	O
prevent	O
against	O
brute-force	O
attacks	O
.	O
</s>
<s>
It	O
is	O
able	O
to	O
run	O
on	O
POSIX	O
systems	O
that	O
have	O
an	O
interface	O
to	O
a	O
packet-control	O
system	O
or	O
firewall	O
installed	O
locally	O
,	O
such	O
as	O
iptables	B-Application
or	O
TCP	B-Protocol
Wrapper	I-Protocol
.	O
</s>
<s>
Fail2ban	B-Protocol
operates	O
by	O
monitoring	O
log	B-Application
files	I-Application
(	O
e.g.	O
</s>
<s>
Most	O
commonly	O
this	O
is	O
used	O
to	O
block	O
selected	O
IP	B-Protocol
addresses	I-Protocol
that	O
may	O
belong	O
to	O
hosts	B-Device
that	O
are	O
trying	O
to	O
breach	O
the	O
system	O
's	O
security	O
.	O
</s>
<s>
It	O
can	O
ban	O
any	O
host	O
IP	B-Protocol
address	I-Protocol
that	O
makes	O
too	O
many	O
login	O
attempts	O
or	O
performs	O
any	O
other	O
unwanted	O
action	O
within	O
a	O
time	O
frame	O
defined	O
by	O
the	O
administrator	O
.	O
</s>
<s>
Fail2ban	B-Protocol
is	O
typically	O
set	O
up	O
to	O
unban	O
a	O
blocked	O
host	O
within	O
a	O
certain	O
period	O
,	O
so	O
as	O
to	O
not	O
"	O
lock	O
out	O
"	O
any	O
genuine	O
connections	O
that	O
may	O
have	O
been	O
temporarily	O
misconfigured	O
.	O
</s>
<s>
Fail2ban	B-Protocol
can	O
perform	O
multiple	O
actions	O
whenever	O
an	O
abusive	O
IP	B-Protocol
address	I-Protocol
is	O
detected	O
:	O
update	O
Netfilter/iptables	B-Application
or	O
PF	B-Protocol
firewall	I-Protocol
rules	O
,	O
TCP	B-Protocol
Wrapper	I-Protocol
's	O
table	O
,	O
to	O
reject	O
an	O
abuser	O
's	O
IP	B-Protocol
address	I-Protocol
;	O
email	O
notifications	O
;	O
or	O
any	O
user-defined	O
action	O
that	O
can	O
be	O
carried	O
out	O
by	O
a	O
Python	B-Language
script	I-Language
.	O
</s>
<s>
The	O
standard	O
configuration	O
ships	O
with	O
filters	O
for	O
Apache	B-Application
,	O
Lighttpd	B-Protocol
,	O
sshd	B-Protocol
,	O
vsftpd	O
,	O
qmail	B-Application
,	O
Postfix	B-Application
and	O
Courier	B-Protocol
Mail	I-Protocol
Server	I-Protocol
.	O
</s>
<s>
Filters	O
are	O
defined	O
by	O
Python	B-Language
regexes	B-Language
,	O
which	O
may	O
be	O
conveniently	O
customized	O
by	O
an	O
administrator	O
familiar	O
with	O
regular	B-Language
expressions	I-Language
.	O
</s>
<s>
As	O
well	O
as	O
the	O
examples	O
that	O
are	O
distributed	O
with	O
the	O
software	O
,	O
a	O
"	O
jail	O
"	O
may	O
be	O
created	O
for	O
any	O
network-facing	O
process	O
that	O
creates	O
a	O
log	B-Application
file	I-Application
of	O
access	O
.	O
</s>
<s>
Fail2ban	B-Protocol
can	O
be	O
integrated	O
with	O
many	O
APIs	B-Application
,	O
including	O
blocklist.de	O
and	O
AbuseIPDB	O
.	O
</s>
<s>
Fail2ban	B-Protocol
fails	O
to	O
protect	O
against	O
a	O
distributed	O
brute-force	O
attack	O
.	O
</s>
<s>
There	O
is	O
no	O
interaction	O
with	O
application-specific	O
APIs	B-Application
.	O
</s>
