In Linux and Unix operating system, it’s possible to use “last” command to display and show the last logged in (and out) users history, and “lastb” command to show and display all the bad login attempts. The users’ login history is been logged and saved in wtmp file while faild login attempts is been stored in btmp file, both files usually located in /var/log directory.
The logging of information into wtmp and btmp is continuous, and can potentially make the wtmp and btmp files grow very to a very big size. The situation is especially true to btmp, which logs failed or bad login attemps to the system, if the administrator does not disable FTP or SSH password authentication, and the server is been attacked via brute-force breaking in attempts, where any wrong user name or incorrect password been logged to btmp.
