The rule detects SSL certificates that utilize Punycode in their domain names, specifically looking for email domains of the SSL issuer that contain the prefix 'xn--'. This prefix indicates the use of internationalized domain names (IDNs) which may be leveraged for domain spoofing and phishing attacks. By querying the Certificates data model in Splunk, the rule identifies relevant SSL certificates and applies CyberChef to decode the Punycode values, revealing their actual domain representations. This is critical as attackers can utilize Punycode to craft deceptive domain names that can trick users and systems into thinking they are communicating with legitimate entities, ultimately leading to unauthorized access or data breaches. To implement this detection effectively, it is essential to have the Certificates data model properly populated and to utilize CyberChef for decoding, or alternatively, skip decoding if not necessary. Caution should be exercised to assess for false positives, especially for organizations interacting with international clients who may legitimately use Punycode domains.