  This paper discusses various observations on beam-induced and cosmic-ray
backgrounds in the ATLAS detector during the LHC 2012 proton-proton run.
Building on published results based on 2011 data, the correlations between
background and residual pressure of the beam vacuum are revisited. Ghost charge
evolution over 2012 and its role for backgrounds are evaluated. New methods to
monitor ghost charge with beam-gas rates are presented and observations of LHC
abort gap population by ghost charge are discussed in detail. Fake jets from
colliding bunches and from ghost charge are analysed with improved methods,
showing that ghost charge in individual radio-frequency buckets of the LHC can
be resolved. Some results of two short periods of dedicated cosmic-ray
background data-taking are shown; in particular cosmic-ray muon induced fake
jet rates are compared to Monte Carlo simulations and to the fake jet rates
from beam background. A thorough analysis of a particular LHC fill, where
abnormally high background was observed, is presented. Correlations between
backgrounds and beam intensity losses in special fills with very high $\beta^*$
are studied.
