lastb
TLDR
List failed login attempts
$ sudo lastb
List failed logins since a date$ sudo lastb -s [YYYY-MM-DD]
List failed logins until a date$ sudo lastb -t [YYYY-MM-DD]
List failed logins at a specific time$ sudo lastb -p [hh:mm]
Resolve IPs to hostnames$ sudo lastb -d
SYNOPSIS
lastb [options] [username]
DESCRIPTION
lastb is the same as last, but shows failed login attempts as recorded in /var/log/btmp. It is useful for security auditing to identify brute force attacks or unauthorized access attempts.
The output shows username attempted, terminal, source address, and timestamp of each failed login.
PARAMETERS
-s, --since TIME
Show records since specified time-t, --until TIME
Show records until specified time-p, --present TIME
Show records at specified time-d, --dns
Translate IP addresses to hostnames-n, --limit NUM
Limit output to NUM records-i, --ip
Display IP addresses
CAVEATS
Requires root privileges to read /var/log/btmp. The btmp file can grow large under attack; log rotation is recommended. File may not exist if never written to.
HISTORY
lastb provides security auditing for failed logins, complementing the last command. The btmp file format mirrors wtmp but records failures instead of successful logins.
