SEABORGIUM is a highly persistent threat actor, frequently targeting the same organizations over long periods of time. Once successful, it slowly infiltrates targeted organizations’ social networks through constant impersonation, rapport building, and phishing to deepen their intrusion. SEABORGIUM has successfully compromised organizations and people of interest in consistent campaigns for several years, rarely changing methodologies or tactics. Based on known indicators of compromise and actor tactics, SEABORGIUM overlaps with the threat groups tracked as Callisto Group (F-Secure), TA446 (Proofpoint) and COLDRIVER (Google). Security Service of Ukraine (SSU) has associated Callisto with Gamaredon Group (tracked by Microsoft as ACTINIUM); however, MSTIC has not observed technical intrusion links to support the association.