The Group-IB Threat Intelligence team has identified HOLLOWGRAPH, a new malware sample that we attribute, with high confidence, to the Cavern backdoor framework. This malware is one component of a larger toolkit, and it uses the Microsoft Graph API through a compromised Microsoft 365 account observed in Israel to communicate with its operators — a technique that helps conceal command-and-control traffic within legitimate Microsoft 365 communications.
The malware supports just two commands, get and send, and executes both exclusively through trusted Microsoft cloud infrastructure. Using the Microsoft Graph API, it treats the compromised mailbox’s calendar as a two-way dead-drop: operators plant tasking as calendar events, and the implant exfiltrates stolen files by creating its own events with encrypted data attached. To avoid catching the mailbox owner’s attention, every event is dated far into the future — 13 May 2050 — with payloads attached as files to the event.
Read more…
Source: Group-IB
Sign up for the Cyber Security Review Newsletter
The latest cyber security news and insights delivered right to your inbox
Related:
- Infiniti Stealer: A new macOS infostealer using ClickFix and Python/Nuitka
March 26, 2026
A previously undocumented macOS infostealer has surfaced during our routine threat hunting. Malwarebytes Labs researchers initially tracked it as NukeChain, but shortly before publication, the malware’s operator panel became publicly visible, revealing its real name: Infiniti Stealer. This malware is designed to steal sensitive data from Macs. It spreads through a fake CAPTCHA page that tricks ...
- Cloud Phones: The Invisible Threat
March 25, 2026
What began as a simple scheme to inflate social media metrics has evolved into a sophisticated threat that is quietly reshaping the economics of digital fraud. Over the past decade, fraud prevention teams have invested heavily in device fingerprinting and emulator detection and that investment paid off; classic emulators and bot activities became predictable, easy ...
- Millions possibly affected by data breach at dermatology giant QualDerm
March 25, 2026
Dermatology management services giant QualDerm suffered a cyberattack in late 2025 which saw it lose sensitive personal and healthcare data on more than three million people. The company is now notifying affected individuals by mail, noting in a breach notification letter that between December 23 and 24, 2025, a threat actor managed to access “a limited ...
- AI Drives Cyber Attacks That Unfold in Minutes
March 24, 2026
Artificial intelligence is speeding up timelines for cyber attacks, a new report has found, creating what the authors call a widening “cybersecurity speed gap” between bad actors and defense efforts. The report from Booz Allen Hamilton, published this month, shows that cyber criminals are now moving from initial access to broader system compromise in less than ...
- Russian initial access broker who fed ransomware crews gets 81 months in US prison
March 24, 2026
A Russian national who sold the keys to corporate networks faces nearly seven years in a US prison after prosecutors tied his handiwork to a string of ransomware attacks costing victims millions of dollars. Aleksei Volkov, 26, was sentenced to 81 months behind bars for his role as an initial access broker, a behind-the-scenes operator who ...
- Google Authenticator: The Hidden Mechanisms of Passwordless Authentication
March 23, 2026
Passwordless authentication is often presented as the end of account takeover. But to understand the real threat landscape, we need to examine how passwordless is actually deployed in the real world. Attackers do not break protocols in theory. They target the most common implementations, the places where usability, scale and architecture intersect. Focusing on one of ...