This detection rule focuses on identifying malicious messages that contain links to 'smartadserver.com', a domain which has been exploited for phishing and malware delivery in the past. The rule introduces a couple of key checks to minimize false positives while capturing risky communications. The first check limits the number of links to less than 15 to enhance the detection capability for potentially malicious content. If any links are detected that lead to 'smartadserver.com' and contain the parameter 'go=' in their query string, the rule examines further to ensure that this go parameter does not lead back to the same domain, filtering out legitimate links. Additionally, the rule checks the headers to confirm that the message does not originate from the 'smartadserver.com' domain. It also includes a verification step against trusted sender domains where if the sender belongs to a high trust list, it must fail DMARC authentication to be flagged. This multi-faceted approach helps in accurately identifying threats associated with credential phishing and malware distribution, relying on sender analysis and detailed URL analysis as its primary detection methods.