/etc/apt/preferences
----------------------
Package: *
Pin: release o=Debian,a=stable,l=Debian-Security
Pin-Priority: 950 

Package: *
Pin: release o=Debian,a=stable
Pin-Priority: 900

Package: *
Pin: release o=Backports.org archive,a=etch-backports
Pin-Priority: 800

Package: *
Pin: release o=Debian,a=testing
Pin-Priority: 700

Package: *
Pin: release o=Debian,a=unstable
Pin-Priority: 600

Package: *
Pin: origin ""
Pin-Priority: 400