Microsoft has tied STRONTIUM to a newly uncovered pattern of Office365 credential harvesting activity aimed at US and UK organizations directly involved in political elections. Analysts from Microsoft Threat Intelligence Center (MSTIC) and Microsoft Identity Security have been tracking this new activity since April 2020. Credential harvesting is a known tactic used by STRONTIUM to obtain valid credentials that enable future surveillance or intrusion operations. Subsequent analysis revealed that between September 2019 and June 2020, STRONTIUM launched credential harvesting attacks against tens of thousands of accounts at more than 200 organizations. In the two weeks between August 18 and September 3, the same attacks targeted 6,912 accounts belonging to 28 organizations. None of these accounts were successfully compromised.

Not all the targeted organizations were election-related. However, we felt it important to highlight a potential emerging threat to the 2020 US Presidential Election and future electoral contests in the UK.

Microsoft CVP Customer Security and Trust, Tom Burt provided some additional details on this campaign in his recent On The Issues blog post. The purpose of this post is to provide defenders in any organization, but especially those directly or indirectly affiliated with electoral systems, insight into the technical nature of this activity. By providing these details, we hope to enable better defense against future attacks and share best practices for securing cloud environments against this type of activity.

Tactical Details

STRONTIUM relied heavily upon spear phishing in its credential harvesting efforts leading up to the 2016 US presidential election. In 2016, spear-phishing was the most common tactic for stealing credentials from targeted accounts. This time around, STRONTIUM appears to be taking a different approach, namely, brute-force/password-spray tooling. This shift in tactics, also made by several other nation-state actors, allows them to execute large-scale credential harvesting operations in a more anonymized manner. The tooling STRONTIUM is using routes its authentication attempts through a pool of approximately 1,100 IPs, the majority associated with the Tor anonymizing service. This pool of infrastructure has evolved over time, with an average of approximately 20 IPs added and removed from it per day. STRONTIUM’s tooling alternates its authentication attempts amongst this pool of IPs approximately once per second. Considering the breadth and speed of this technique, it seems likely that STRONTIUM has adapted its tooling to use an anonymizer service to obfuscate its activity, evade tracking, and avoid attribution.

Strontium, operating from Russia, has attacked more than 200 organizations including political campaigns, advocacy groups, parties and political consultants

Zirconium, operating from China, has attacked high-profile individuals associated with the election, including people associated with the Joe Biden for President campaign and prominent leaders in the international affairs community

Phosphorus, operating from Iran, has continued to attack the personal accounts of people associated with the Donald J. Trump for President campaign