How were the anti-fraud rules implemented at the service level?

Anti-fraud rules at the service level are usually implemented through a set of checks and filters that analyze incoming requests and transactions in real time. In Golang, this can be implemented using middleware that intercepts requests and applies rules, for example:

• Checking request frequency from a single IP or account (rate limiting)
• Analyzing anomalies in user behavior (e.g., sudden changes in purchase patterns)
• Validating data for suspicious values
• Using blacklists and whitelists

An example of simplified middleware for request frequency checking:

func AntiFraudMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        userID := r.Header.Get("X-User-ID")
        if isSuspicious(userID) {
            http.Error(w, "Request blocked by anti-fraud rules", http.StatusForbidden)
            return
        }
        next.ServeHTTP(w, r)
    })
}

func isSuspicious(userID string) bool {
    // Logic for checking, e.g., request frequency
    return false
}

Thus, anti-fraud rules are integrated into the service as part of request processing, allowing for prompt blocking of suspicious activities.