If you just want to flip some setting to "best practice", look
into lynis.

Debian wiki keeps a fair privacy/security step-by-step guide you
may enjoy:
https://wiki.debian.org/SetupGuides/SecurePersonalComputer

The now dead Crunchbang forums had a dear guide/thread too, but
it's very dated. It does a good job introducing concepts so it's
a good read, but exercise caution taking any advice from it - some
of the shortcoming are less obvious than recommended software being
deprecated everywhere (ipkungfu... they'd probably recommend ufw today)
https://web.archive.org/web/20220921120218/https://crunchbang.org/forums/viewtopic.php?id=24722

Don't know any intermediate guides, seems like there's a shortage of
these in IT in general.

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