If they don't get you online, they'll try in person. A data-theft and extortion gang has targeted “dozens” of banks, law firms, and other professional services companies in the US from January through May, using fake help desk calls and other social-engineering techniques to gain access to corporate IT environments, according to Google’s Mandiant incident response team. And when those remote-deception methods don’t work, the criminals sometimes show up at victims’ physical offices, posing as IT technicians, and attempt to steal sensitive files using thumb drives.Google’s threat hunters track the extortion threat group as UNC3753, while other analysts call it Luna Moth, Chatty Spider, and Silent Ransom Group. The crew has been around since 2022, originally using fake software renewal emails and other billing lures, typically with PDF attachments containing phone numbers for attacker-controlled call centers, as their means of gaining initial access to corporate networks.
Beginning around March 2025, the crims shifted tactics and started posing as IT help desk staff.“While UNC3753 primarily relies on digital vectors, GTIG assesses that associated threat actors have also attempted direct data theft using physical, in person access,” Google incident responders and researchers Chad Reams, Tufail Ahmed, Keith Knapp, Ashley Frazer, and Tyler McLellan said in a Friday blog.The authors also pointed to a May FBI alert to corroborate this in-person tactic. According to the feds, Silent Ransom Group crooks have been walking into law firms’ physical offices as recently as this spring. Once they are on-site, they claim to be IT support staff needing to image a device or create local backups for security reasons. If that line works, they plug a thumb drive into the victim’s computer and steal data the old-fashioned way.“Although limited forensic evidence and the absence of a subsequent extortion attempt prevent formal attribution, GTIG assesses that these physical intrusions are likely associated with UNC3753 based on structural, timeline, and targeting overlaps,” the blog said.Google won’t say how many dozens of firms have been targeted in these attacks, or how many ended in the data thieves paying a visit to the victims’ locations. “While we can’t share additional details regarding specific investigations, Mandiant CTO Charles Carmakal notes that this tactic has been observed over the years,” a spokesperson told The Register. “Mandiant has investigated various matters where adversaries planted insiders, bribed employees, or physically entered buildings to facilitate cyberattacks.”Another noteworthy thing about UNC3753’s attacks: they are very fast. In many of Mandiant’s investigated incidents, the entire operation from initial contact to data extortion occurred in just one day. “Recently, Mandiant observed data searches, staging, and theft initiated in under an hour,” the threat analysts warned.
