It is not a good thing to have a weak default (other) entry. This service is the default configuration for all PAM aware applications and if it is weak, your system is likely to be vulnerable to attack.
Here is a sample "other" configuration file. The pam_deny module will deny access and the pam_warn module will send a syslog message to auth.notice:
#
# The PAM configuration file for the `other' service
#
auth required pam_deny.so
auth required pam_warn.so
account required pam_deny.so
account required pam_warn.so
password required pam_deny.so
password required pam_warn.so
session required pam_deny.so
session required pam_warn.so