From bleepingcomputer.com
A newly discovered and uncommonly stealthy Advanced Persistent Threat (APT) group is breaching corporate networks to steal Exchange (on-premise and online) emails from employees involved in corporate transactions such as mergers and acquisitions.
Mandiant researchers, who discovered the threat actor and now track it as UNC3524, say the group has demonstrated its “advanced” capabilities as it maintained access to its victims’ environments for more than 18 months (in some cases).