Microsoft has been monitoring these attacks and notifying targeted customers for several months, but only recently reached a point in our investigation where we can attribute the activity to Strontium with high confidence. MSTIC’s investigation revealed that Strontium has evolved its tactics since the 2016 election to include new reconnaissance tools and new techniques to obfuscate their operations. In recent months, it has engaged in brute force attacks and password spray, two tactics that have likely allowed them to automate aspects of their operations. Strontium also disguised these credential harvesting attacks in new ways, running them through more than 1,000 constantly rotating IP addresses, many associated with the Tor anonymizing service. Strontium even evolved its infrastructure over time, adding and removing about 20 IPs per day to further mask its activity