A trusted third party notified the Department of Homeland Security United States National Cybersecurity & Communications Integration Center (NCCIC) that one or more machines on your network was infected with malware associated with the  Avalanche botnet infrastructure during December 2016. Avalanche is a large global network hosting infrastructure used by cyber criminals to conduct phishing and malware distribution campaigns and money mule schemes.
A system infected with Avalanche associated malware may be subject to malicious activity including the theft of user credentials and other sensitive data, such as banking and credit card information. Some of the malware has the  capability to encrypt user files and demand a ransom be paid by the victim to regain access to those files. In addition, the malware may allow criminals unauthorized remote access to the infected computer. Infected systems could be  used to conduct distributed denial-of-service (DDoS) attacks.  For additional information, please see the following US-CERT Technical Alert (TA16-336A):  https://www.us-cert.gov/ncas/alerts/TA16-336A