Which type of symptoms might involve anonymous complaints about a buyer?

Anonymous complaints about a buyer are indicative of document symptoms, as these complaints often arise from discrepancies or irregularities that may be found in documentation related to the buyer's transactions or behaviors. Document symptoms refer to issues that can be identified through the examination and analysis of records, such as contracts, invoices, or communication logs. These documents may reveal inconsistencies or suggestive evidence of fraudulent activity, prompting individuals to make complaints about the buyer anonymously.

In this context, complaints might serve as a red flag highlighting potential fraud or unethical behaviors that require further investigation, often supported by documented evidence. The nature of these complaints is typically tied to identifiable features in the documentation that raise suspicion.

Other types of symptoms, such as lifestyle, control, or behavioral symptoms, typically concern different aspects of fraud detection. Lifestyle symptoms might highlight excessive or extravagant living that isn’t supported by one’s known salary or income, while control symptoms often relate to unusual or excessive control over transactions, processes, or records by a specific individual. Behavioral symptoms may indicate changes in an individual’s behavior, such as increased defensiveness or secrecy about their work, which may not directly connect to anonymous complaints. Therefore, the focus on documentation makes "document symptoms" the most appropriate choice in this scenario.