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Threat Assessment: Ryuk Ransomware
Unit 42 assesses Ryuk ransomware amid a CISA/FBI/HHS alert on threats to U.S. healthcare, including the UHS attack that disrupted hospital operations.
A joint CISA, FBI, and HHS alert on October 28, 2020 warned of an imminent threat to U.S. healthcare from operators deploying Trickbot and Ryuk ransomware. Universal Health Services reported a Ryuk attack that disrupted all U.S. UHS sites for weeks, with similar incidents at hospitals in Oregon and New York. Ryuk typically arrives after Trickbot or BazaLoader infections delivered via malicious email, and operators enumerate networks with PowerShell and WMI before encryption. The Trickbot Anchor_DNS module performs DNS tunneling for C2, using connectivity checks to benign domains like ipinfo.io and checkip.amazonaws.com.
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Gigabud Creates Android Work Profiles to Hide From Banking App Malware Checks
Group-IB reports the Gigabud Android banking trojan uses a cloned work profile to hide from banking app malware checks, with infections confirmed in Indonesia.
Group-IB says Gigabud installs a helper app called Vwork, derived from the open-source Shelter tool, which creates an Android work profile and drops a tampered banking app inside it, hiding the trojan from banking apps' malware scans. Gigabud, active since 2022 and linked by Group-IB to the GoldFactory group, abuses Accessibility access and overlay screens to steal credentials and run fraudulent payments while a black screen conceals the operator's actions. Group-IB confirmed the full attack chain on infected devices in Indonesia, counting about 1,469 compromised devices and estimated losses of roughly $960,000 between February and July 2026. Vwork-compatible Gigabud samples have been found targeting 11 countries including Brazil, Mexico, Indonesia, Thailand, and Türkiye, though only the Indonesian chain is confirmed.
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Autoencoder Is All You Need: Profiling and Detecting Malicious DNS Traffic
Palo Alto Unit 42 details an autoencoder-based method that profiles DNS traffic to detect C2 and malicious domains, blocking ~374,000 malicious DNS requests daily.
Unit 42 built an RNN-based autoencoder that compresses DNS traffic time series into fixed-dimensional 'DNS profiles' for each domain and device. Downstream classification, clustering, and anomaly detection modules flag suspicious domains, capturing 170 emerging suspicious domains in May 2024. Signatures block roughly 374,000 malicious DNS requests daily and run in the Advanced DNS Security service, with detections shared to Advanced URL Filtering. Case studies link DNS traffic patterns to C2 beaconing, dynamic DNS abuse, and DNS tunneling for data exfiltration.
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Threat Brief: Maze Ransomware
Unit 42 issued a threat brief on Maze ransomware, noting an uptick across industries and exploitation of Pulse VPN and IE flaws for initial access.
Palo Alto Networks detected an uptick in Maze ransomware samples across finance, healthcare, government, and other sectors. Maze, a variant of ChaCha ransomware first seen in May 2019, is distributed via weaponized Word/Excel attachments and the Spelevo exploit kit leveraging CVE-2018-15982 and CVE-2018-4878, and has used CVE-2019-11510 (Pulse VPN) and CVE-2018-8174 (Internet Explorer). Operators establish a foothold, escalate privileges, move laterally, and exfiltrate files before encryption for extortion leverage.
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GoldFactory Weaponizes Open-Source Vwork App Cloner in Gigabud Banking Malware Attacks
Group-IB says GoldFactory's Gigabud Android trojan uses Vwork, a weaponized Shelter fork, to clone banking apps into isolated Work Profiles and evade bank-side detection.
Group-IB's 'Hook for Gold' investigation found GoldFactory ships Vwork, a modified fork of the open-source Shelter app, alongside its Gigabud Android banking trojan, active since 2022. Vwork abuses Android Work Profile provisioning to clone banking apps into an isolated environment, weakening the link between detected malware signals and fraudulent transactions. Gigabud has targeted victims in Southeast Asia, Latin America, the Middle East, Africa, and beyond via fake airline, tax, and government apps requesting Accessibility and overlay permissions. In Indonesia, telemetry recorded about 1,469 compromised devices and roughly $960,939 in estimated losses between February and July 2026.
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