The rule is designed to detect DNS tunneling, a technique used by attackers to bypass security controls and exfiltrate data using DNS as a covert channel. It calculates the total length of DNS queries and answers and looks for unusually high volume traffic, which can suggest tunneling activity. The detection method includes filtering out legitimate DNS queries from internal systems and services such as DNS servers, web proxies, and email servers, thereby minimizing false positives. However, this rule has been deprecated, as similar functionalities are now addressed through other rules like 'ESCU - DNS Query Length Outliers - MLTK - Rule' and 'ESCU - DNS Query Length With High Standard Deviation - Rule'.