1. A method for network risk assessment, comprising: receiving, by a processor, data describing a network, wherein the network includes a plurality of entities and links describing relationships between the plurality of entities; identifying a set of seed entities from the plurality of entities based on predefined rules; generating a set of sub-networks based on the set of identified seed entities, wherein each sub-network includes at least one seed entity and one or more other entities of the plurality of entities having at least one link to the at least one seed entity; calculating a risk score for each of the generated sub-networks; generating a plurality of sets of sub-networks iteratively by: a) identifying an Nth set of seed entities from the plurality of entities, based on the risk scores calculated for the N−1 set of sub-networks; b) generating an Nth set of sub-networks based on the identified Nth set of seed entities; and c) calculating the risk scores for each of the sub-networks in the Nth set; and repeating steps a) through c) until a stopping condition is reached, wherein a lower threshold and upper threshold define a range and the stopping condition is reached when the risk scores of the entities are less than a lower threshold or greater than an upper threshold; and providing a fraud alert regarding whether one of the entities or sub-network is at risk for suspicious financial activity either when a respective calculated risk score is below a risk score threshold or when a respective calculated risk score is above a risk score threshold.