  We propose that observations of "hidden" magnetars in central compact objects
can be used to probe crustal activity of neutron stars with large internal
magnetic fields. Estimates based on calculations by Perna \& Pons (2011), Pons
\& Rea (2012) and Kaminker et al. (2014) suggest that central compact objects,
which are proposed to be "hidden" magnetars, must demonstrate flux variations
on the time scale of months-years. However, the most prominent candidate for
the "hidden" magnetars --- CXO J1852.6+0040 in Kes 79, -- shows constant
(within error bars) flux. This can be interpreted by lower variable crustal
activity than in typical magnetars. Alternatively, CXO J1852.6+0040 can be in a
high state of variable activity during the whole period of observations. Then
we consider the source 1E161348-5055 in RCW103 as another candidate. Employing
a simple 2D-modeling we argue that properties of the source can be explained by
the crustal activity of the magnetar type. Thus, this object may be
supplemented for the three known candidates for the "hidden" magnetars among
central compact objects discussed in literature.
