Arch Linux

I have sshd running on the server.
There are many ssh login attempts (brute force) logged in /var/log/auth.log.
But with every login attempt there is also a message:
Excess permission or bad ownership on file /var/log/btmp

So, sshd complains about permissions to this file which are:
ls -l /var/log/btmp
-rw-r--r-- 1 root root 0 2004-11-14 17:34 /var/log/btmp

This also makes lastb command (shows failed login attempts) useless becasue it's using an empty btmp file.

I've googled around and found similar redhat bug report:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=156900
with a workaround:
chmod 0600 /var/log/btmp

I've tried it and it seems to work. Simulated failed login is now beeing printed by lastb command.

pacman -Qo /var/log/btmp returns:
No package owns /var/log/btmp

so I don't know when and by what this file is created (it's possible that it was created just by using lastb command for the first time but the date is quite old).

There is also a security risk if /var/log/btmp is world readable. Other programs may accept current permissions and the common mistake is to use password in place of a login name which will be logged in this file too and available for all users :-)