Content processing includes receiving a set of a correctly spelled alert words and at least one spelling variant corresponding to each correctly spelled alert word; determining at least one alignment of joint multigrams for each correctly spelled alert word/corresponding spelling variant pair; training a model of correspondence between the set of received orthographic alert words and corresponding spelling variants using the determined alignments; and receiving a spelling variant observation from a content block. Using the trained model, the technology determines a probability that the received spelling variant observation corresponds to a received correctly spelled alert word. For a determined probability exceeding a configured threshold, the technology denies automatic acceptance of the content block.