/etc/login.defs - Configuration control definitions for the login package.
# Enable logging and display of /var/log/faillog login failure info.
# This option conflicts with the pam_tally PAM module.
#
FAILLOG_ENAB yes
#
# Enable display of unknown usernames when login failures are recorded.
#
# WARNING: Unknown usernames may become world readable.
# See #290803 and #298773 for details about how this could become a security
# concern
LOG_UNKFAIL_ENAB no
#
# Enable logging of successful logins
#
LOG_OK_LOGINS no
...
#
# If defined, login failures will be logged here in a utmp format
# last, when invoked as lastb, will read /var/log/btmp, so...
#
FTMP_FILE /var/log/btmp
...
#
# If defined, file which inhibits all the usual chatter during the login
# sequence. If a full pathname, then hushed mode will be enabled if the
# user's name or shell are found in the file. If not a full pathname, then
# hushed mode will be enabled if the file exists in the user's home directory.
#
HUSHLOGIN_FILE .hushlogin
#HUSHLOGIN_FILE /etc/hushlogins
$ man last
DESCRIPTION
Last searches back through the file /var/log/wtmp (or the file desig‐
nated by the -f flag) and displays a list of all users logged in (and
out) since that file was created.
...
Lastb is the same as last, except that by default it shows a log of
the file /var/log/btmp, which contains all the bad login attempts.
...
NOTES
The files wtmp and btmp might not be found. The system only logs
information in these files if they are present. This is a local con‐
figuration issue. If you want the files to be used, they can be cre‐
ated with a simple touch(1) command (for example, touch
/var/log/wtmp).
$ man wtmp
DESCRIPTION
The utmp file allows one to discover information about who is cur‐
rently using the system. There may be more users currently using the
system, because not all programs use utmp logging.
Warning: utmp must not be writable by the user class "other", because
many system programs (foolishly) depend on its integrity. You risk
faked system logfiles and modifications of system files if you leave
utmp writable to any user other than the owner and group owner of the
file.
D’où il ressort qu’il serait possible d’escamoter /var/log/wtmp en ayant conscience de ce qu’il n’y aurait plus de traces.
Les crackers qui réussiraient à déjouer les logins cherchent justement à effacer les traces des tentatives échouées et réussies …