como puedas lea en este manual esa misma fecha data de 2002:
At the end of the installation, you will be asked if shadow passwords
should be enabled. Answer yes to this question, so passwords will be
kept in the file '/etc/shadow'. Only the root user and the group
shadow have read access to this file, so no users will be able to grab
a copy of this file in order to run a password cracker against it.
You can switch between shadow passwords and normal passwords at any
time by using 'shadowconfig'.
Read more on Shadow passwords in Shadow Password
(http://www.linuxdoc.org/HOWTO/Shadow-Password-HOWTO.html)
('/usr/share/doc/HOWTO/en-txt/Shadow-Password.txt.gz').
Furthermore, you are queried during installation whether you want to
use MD5 hashed passwords. This is generally a very good idea since it
allows longer passwords and better encryption. MD5 allows for
passwords longer than 8 characters. This, if used wisely, can make it
more difficult for attackers to brute-force the system's passwords.
Regarding MD5 passwords, this is the default option when installing
the latest 'password' package. You can change this anytime after
installation by doing 'dpkg-reconfigure -plow passwd'. You can
recognize md5 passwords in the '/etc/shadow' file by their $1$ prefix.
This, as a matter of fact, modifies all files under '/etc/pam.d' by
substituting the password line and include md5 in it:
password required pam_unix.so md5 nullok obscure min=6 max=16
If 'max' is not set over 8 the change will not be useful at all. For
more information on this read Section 4.10.1, 'User authentication:
PAM'.
Note: the default configuration in Debian, even when activating MD5
passwords, does not modify the previously set 'max' value.
Esta ya no es la forma predeterminada de hash de las contraseñas en debian.
En el capítulo 4.11.1.1 Seguridad de contraseña en PAM puedo leer que la opción predeterminada es sha512 de Debian Squeeze (2009).
Debe asegurarse de que el módulo pam_unix.so use la opción "sha512" para usar contraseñas cifradas. Este es el valor predeterminado en Debian Squeeze.
La línea con la definición del módulo pam_unix se verá
algo como:
password [success=1 default=ignore] pam_unix.so nullok obscure minlen=8 sha512
El problema con estos manuales es que hay algunas partes que están desactualizadas. La comunidad intenta solucionar este tipo de problemas si los denuncia, y también puede ofrecerse como voluntario para arreglar esa parte de la documentación.