Descriptions of items are offered for sale by one or more merchants in an online marketplace. The online marketplace comprises a website hosted by a server. The descriptions are electronically scanned or otherwise accessed. The scanned descriptions are deconstructed into a plurality of N-grams. Each N-gram includes a combination of words appearing in the descriptions of items. The electronic scan and deconstruction are repeated over a plurality of predefined time periods. For each N-gram, a frequency of occurrence is monitored in each of the predefined time periods. Based on the monitoring, a determination is made that a first N-gram of the plurality of N-grams whose frequency of occurrence has exceeded a predefined threshold in one of the predefined time periods. Risks of transactions involving one or more items whose descriptions contain the first N-gram are evaluated.