This rule detects potential usage of the Encrypting File System Remote Protocol (MS-EFSRPC), which has been associated with the PetitPotam attack. The Mitigated usage of this RPC is expected to be very rare in typical network environments, thus any detected operation that begins with 'efs' is indicative of potential malicious behavior requiring further investigation. Administrators should analyze surrounding logs from the same source IP to corroborate legitimacy, focusing on other protocols like dce_rpc, smb_mapping, rdp, ntlm, and kerberos during the time frame before and after the detection.