  We present an analysis of the faint M star population seen as foreground
contaminants in deep extragalactic surveys. We use space-based data to separate
such stars from high redshift galaxies in a publically-available dataset, and
consider the photometric properties of the resulting sample in the optical and
infrared. The inferred distances place these stars well beyond the scale height
of the thick disk. We find strong similarities between this faint sample
(reaching i'_{AB}=25) and the brighter disk M dwarf population studied by other
authors. The optical-infrared properties of the bulk of our sources spanning
6000A-4.5microns are consistent with those 5-10 magnitudes brighter. We also
present deep spectroscopy of faint M dwarf stars reaching continuum limits of
i'_{AB}~26, and measure absorption line strengths in the CaH2 and TiO5 bands.
Both photometrically and spectroscopically, our sources are consistent with
metallicities as low as a tenth solar: metal-rich compared with halo stars at
similar heliocentric distances. We comment on the possible MACHO identification
of M stars at faint magnitudes.
