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Linux How do I display failed login attempt?

/var/log/faillog is a log file for failed login attempts. This file maintains a count of login failures and the limits for each account. The file is fixed length record, indexed by numerical ID. Each record contains the count of login failures since the last successful login; the maximum number of failures before the account is disabled; the line the last login failure occurred on; and the date the last login failure occurred. Since data is in binary format you need to use faillog command to display failed login attempt.

How do I use faillog?

To display failed login attempt for user root with following command:
$ faillog -u root

Login       Failures Maximum Latest                   On
root            0        0   02/17/06 14:49:52 +0530  tty1

To display all failed login attempt try:
$ faillog -a

Login       Failures Maximum Latest                   On
root            0        0   02/17/06 14:49:52 +0530  tty1
rocky           0        0   02/27/06 22:05:03 +0530  tty1
usr1            2        0   02/16/06 15:05:01 +0530  tty2

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Linux Iptables block all network traffic

You would like to block all network traffic using iptables firewall under Debian GNU/Linux. This will block all incoming and outgoing traffic including Internet aka ADSL/ppp0 and it is highly recommend. The logic is block everything and allow only required traffic. This can be done with four simple commands:

# iptable -F
# iptables -P INPUT DROP
# iptables -P OUTPUT DROP
# iptables -P FORWARD DROP

Please do not enter above command over remote ssh login session.