Oliver (2014): The paper is a literature review, so it’s a good starting point for identifying relevant material.
Oliver (2014:1): Covert groups do not leave organisational charts. What they do leave is evidence of communications, kinship ties, co-participation in events. In other words, relational data.
Oliver (2014:1): Work often focused on resilience and disruption. Methodologically, on link prediction, boundary definition, and missing data.
Oliver (2014:1): "A common factor to all covert networks is the need or wish to remain secret; although what is to be kept secret and from whom differs, and indeed is rarely specified” See also Crossly et al. 2010. Covert not likely to be binary, and there are consequences for revealing that which people try to keep hidden. Covert and illegal are not synonymous.
Oliver (2014:3): "A reasonable assumption would be that covert networks are so because membership or activities are kept secret. For example, members may wish to achieve ends which must be kept secret (e.g. purchasing sex or drugs); or activities which further those ends much [sic] be kept secret (such as individual acts of terrorism in a global Jihad).”
An important question is therefore: What is a covert network?’ A related question is ‘why is the network covert?'
Oliver (2014:3): What may be kept secret: Identities, aims, activities.
Oliver (2014): Some questions addressed by the literature on covert networks: what is the role of existing ties on network formation and existence? Do prior ties increase the resilience of those ties? What is the role of trust? To what degree are covert networks embedded within overt networks? Do networks segregate as they become covert? How much time is spent on covers activities (absorption)? What is the effectiveness of networks? And, relatedly, what impact do different types of tie have an effectiveness? How resilient are networks?
Oliver (2014): Another question that emerges is the degree to which aims affect network structure. Some scholars explicitly argue that they do, e.g. decentralised strictures.
Oliver (2014: 11-12):
Oliver (2014: 13):
Oliver (2014): How are people recruited to covert networks? Various theories - covert networks form through fragmentation or factioning, recruitment relies on pre-existing ties - have been proposed but not empirically tested.
Oliver (2014:19): “there is a lack of comparable empirical data in the field, and that theories about some types of covert network, even if empirically verified may not be generalizable to other types.”