The rule 'Anthropic Magic String in HTML' is designed to detect messages that contain the specific string 'ANTHROPIC_MAGIC_STRING' in multiple parts of the message content. The rule evaluates inbound messaging, particularly focusing on the plain text and HTML body content. It checks various formats including the raw HTML content, the raw plain text content, and the display text of the HTML. Additionally, it scans attachments for the specified string using Optical Character Recognition (OCR) and string analysis methods on the extracted content of the attachments. The inclusion of attachments is limited to a maximum of three, which ensures that the detection remains efficient. Given its ability to identify malware or ransomware-related communications through this specific string, it serves as a critical component of content analysis in threat detection. By leveraging this rule, organizations can proactively defend against potential exploits that may utilize the identified magic string as part of their attack vector.