The AWS EC2 Multi Instance Connect rule detects unauthorized attempts to push an SSH public key to multiple Amazon EC2 instances, a potential indicator of lateral movement by attackers. This rule monitors AWS CloudTrail logs for the 'SendSSHPublicKey' event from the EC2 Instance Connect service. If an SSH public key is sent successfully to at least two EC2 instances within a designated period, an alert is generated due to the high potential threat this behavior may pose. Attackers could utilize this technique to gain wider access to an organization’s resources, making it critical to have adequate monitoring and response mechanisms in place. Administrators should review the reasoning behind multiple instances receiving the same key and verify the actor's identity while considering implementing unique keys for each instance to enhance security. This rule is crucial for maintaining the integrity of cloud environments by detecting and responding to lateral movement tactics.