While the author, Dante (who is also the protagonist) obviously denounces fraud as denying or openly contradicting the truth, his contempt for it runs deeper than that. The root of fraud is linguistic sin and because man’s unique gift is language, human beings seem particularly susceptible to fraud. As one of the fundamental unifying bonds in society – uniting individuals and facilitating communication – language holds a high status in Dante’s eyes. The fraudulent, by corrupting language, threaten to compromise the cohesiveness of society. Unlike incontinence and violence, which affect only the agent or his victim, fraud has the ability to deceive whole communities of people – even institutions like the Church and entire cities like Florence.
Fraud is considered a more wicked sin than incontinence or violence because it compromises universal human connections like language and money and has the ability to dupe whole communities of people, instead of harming only the individual committing the fraud.
Based on Geryon’s appearance and the metaphorical language with which Dante surrounds his description, the beast clearly represents the sin of fraud.