tiger always reports "no password" with NIS

["Sebastian Haase" <haase@msg.ucsf.edu>]

Hi !
I installed tiger to have some checks on my security sone:
But everyday I get messages like these:
# Performing check of user accounts...
# Checking accounts from /etc/passwd.
--WARN-- [acc011w] Login ID +alexis does not have a password.

That is: I use NIS and have specific users maked with a '+' - sign in
/etc/passwd
like this:
+alexis::0:0:::

Isn't this a correct way of 'nis-sifying' certain users !?

Thanks,
Sebastian