LightNeuron is the first to target Microsoft Exchange transport agents and is used as a hub for major Turla APT espionage efforts. The malware has flown under the radar since at least 2014, despite being the malware linchpin at the center of several targeted campaigns. It can spy on, modify or block all emails going through a compromised mail server; and can execute commands sent by email while acting as a full-featured backdoor for remote code-execution. It’s the first publicly known malware to use a malicious Microsoft Exchange Transport Agent.
Source: https://threatpost.com/powerful-lightneuron-malware/144519/