Win64/Sirefef.AN is defined as a Trojan infection which becomes apparently a severe situation to the compromised system. The virus was generated from a multi-component family which can split into system and stay background on an infected computer. The virus has been created to collect private data and connect with a remove server for payloading insanely via social websites. The virus can infect computers in various ways.
How to Safely Clear Win64/Sirefef.AN Virus/ Tips for Trojan Virus Removal