Unit 42 has observed activity over the last 4 months involving the BackConfig malware used by the Hangover threat group (aka Neon, Viceroy Tiger, MONSOON). Targets of the spear-phishing attacks, using local and topical lures, included government and military organizations in South Asia.
The BackConfig custom trojan has a flexible plug-in architecture for components offering various features, including the ability to gather system and keylog information and to upload and execute additional payloads.
The initial infection occurs via a weaponized Microsoft Excel (XLS) document delivered via compromised legitimate websites for which the URLs are most likely shared via email. The documents use Visual Basic for Applications (VBA) Macro code which, if enabled by the victim, starts an installation process consisting of multiple components that result in the plug-in loader payload being downloaded and executed.
Source: Palo Alto