  Eruptions of coronal mass ejections (CMEs) from the Sun are usually
associated with a number of signatures that can be identified in solar disc
imagery. However, there are cases in which a CME that is well observed in
coronagraph data is missing a clear low-coronal counterpart. These events have
received attention during recent years, mainly as a result of the increased
availability of multi-point observations, and are now known as 'stealth CMEs'.
In this work, we analyse examples of stealth CMEs featuring various levels of
ambiguity. All the selected case studies produced a large-scale CME detected by
coronagraphs and were observed from at least one secondary viewpoint, enabling
a priori knowledge of their approximate source region. To each event, we apply
several image processing and geometric techniques with the aim to evaluate
whether such methods can provide additional information compared to the study
of "normal" intensity images. We are able to identify at least weak eruptive
signatures for all events upon careful investigation of remote-sensing data,
noting that differently processed images may be needed to properly interpret
and analyse elusive observations. We also find that the effectiveness of
geometric techniques strongly depends on the CME propagation direction with
respect to the observers and the relative spacecraft separation. Being able to
observe and therefore forecast stealth CMEs is of great importance in the
context of space weather, since such events are occasionally the solar
counterparts of so-called 'problem geomagnetic storms'.
