Malspam is a type of spam email designed to deliver malware payloads via malicious URLs or infected attachment. Spoof emails sent by this malicious campaign’s operators trick hotel employees into opening an attachment disguised as an invoice detailing arrears in the form of outstanding bills with more information on the services and goods that haven’t yet been paid. Security researches from Qihoo 360 Security Center found that the attachments are used to infect the victims’ computers with a NetWiredRC RAT which enables the attackers to gain unauthorized access and steal information.
Source: https://www.bleepingcomputer.com/news/security/hackers-target-the-north-american-hotel-industry-with-a-rat/