This rule is designed to detect the presence of the EICAR test string, which is a standard file for evaluating anti-virus software functionality. It specifically targets attachments that include 'eicar' in their filename to minimize performance impacts during analysis. The detection mechanism implements a search that checks the contents of the attachments, looking for the specific EICAR signature, which is recognizable by the string 'X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*'. This makes the rule particularly effective for validating that anti-virus and file scanning capabilities are correctly identifying test malware without triggering on other files, thereby ensuring the effectiveness and integrity of the scanning process. The rule serves primarily as a testing and validation tool rather than as a proactive malware detection mechanism, given its low severity rating.