This rule detects authentication failures associated with the Label Distribution Protocol (LDP) on Cisco devices, which could signify attempts at unauthorized access through brute force methods to manipulate Multiprotocol Label Switching (MPLS) labels. The detection identifies specific log entries indicating failures in MD5 authentication, which is crucial for securing LDP sessions. If such failures are observed, they may warrant further investigation to rule out potential attacks against MPLS infrastructure. The requirement for this detection rule is that Cisco LDP logs must be enabled and correctly ingested for effective monitoring. The low severity level indicates that while the detection may represent potential threats, these occurrences may also arise from benign misconfigurations. Key keywords related to this rule include `SOCKET_TCP_PACKET_MD5_AUTHEN_FAIL` and `TCPMD5AuthenFail`, which are crucial for triggering the detection logic. Misconfigurations are the primary concern for false positives in this rule, making it highly nuanced in a production environment where LDP configurations must be verified.