Welcome to BlackFile: Inside a Vishing Extortion Operation

Written by: Austin Larsen, Tyler McLellan, Genevieve Stark, Dan Ebreo Introduction Google Threat Intelligence Group (GTIG) has continued to track an expansive extortion campaign by UNC6671, a threat actor operating under the "BlackFile" brand, that targets organizations via sophisticated voice phishing (vishing) and single sign-on (SSO) compromise. By leveraging adversary-in-the-middle (AiTM) techniques to bypass traditional perimeter defenses and multi-factor authentication (MFA), UNC6671 gains deep access to cloud environments.

The group primarily targets Microsoft 365 and Okta infrastructure, leveraging Python and PowerShell scripts to programmatically exfiltrate sensitive corporate data for subsequent extortion attempts. This post details UNC6671’s attack lifecycle and provides defenders with actionable guidance to detect and mitigate these identity-centric threats. Since emerging in early 2026, UNC6671 has maintained a high operational cadence. GTIG assesses that the group has targeted dozens of organizations across North America, Australia, and the UK.

GTIG previously highlighted UNC6671 as a distinct cluster in a prior report detailing similar SaaS data-theft techniques utilized by ShinyHunters (UNC6240). While UNC6671 has co-opted the ShinyHunters brand in at least one instance to inject artificial credibility into their threats, GTIG assesses that the operations are independent. This distinction is supported by UNC6671's use of separate TOX communication channels, unique domain registration patterns, and the launch of a dedicated "BlackFile" data leak site (DLS). These compromises are not the result of a security vulnerability in vendor products or infrastructure.

Instead, this campaign continues to highlight the effectiveness of social engineering and underscores the critical importance of organizations moving toward phishing-resistant MFA to protect their SaaS and identity platforms .