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:
- Mirage Kitten targets Middle East and Africa region with new malware
July 28, 2026
Mirage Kitten – also known as UNC1549, Smoke Sandstorm, and Nimbus Manticore – is an advanced persistent threat (APT) group focused on cyber-espionage operations against aerospace, aviation, defense, and telecommunications sectors across the Middle East and Africa, using highly targeted spear-phishing campaigns, fake recruitment portals, and custom multi-stage malware to gain persistent access and exfiltrate sensitive data. During ...
- Hugging Face CEO calls for ‘radical transparency’ after ‘unprecedented’ OpenAI hack
July 26, 2026
After OpenAI recently admitted that one of its models had breached the systems of AI platform Hugging Face, Hugging Face’s CEO Clem Delangue posted on X that he was flying to San Francisco to have “a little chat with that ‘rogue agent.’” Then, in a follow-up post on Saturday, Delangue outlined what he’d asked for from OpenAI. He said he called ...
- What the First Autonomous Ransomware Case Confirms
July 24, 2026
Security researchers have documented an AI agent running a full ransomware operation on its own against a live production target, planning, adapting, and executing every step from the first exploit through data destruction. This is early real-world evidence of the shift to autonomous criminal operations that our research forecast. Agent-run attacks change what defenders can rely ...
- CISA has expanded the scope of its alert on Iranian-affiliated hackers attacking critical infrastructure
July 23, 2026
The US Cybersecurity and Infrastructure Security Agency (CISA) has expanded the scope of its alert on Iranian-affiliated hackers attacking critical infrastructure, including water and energy facilities. The original advisory focused on programmable logic controllers (PLCs) manufactured by Rockwell Automation/Allen-Bradley. The update warns that the activity may also target devices from Schneider Electric, Siemens, “and potentially other branded/manufactured PLCs.” The conflict between ...
- Millions of cars could be tracked and unlocked by a hidden security flaw
July 23, 2026
A car alarm vendor’s coding mistake has left millions of vehicles vulnerable to theft and location tracking. Thanks to the way dealers sell car alarms, many affected drivers don’t even know they have one installed. The device is the KARR Security System, a Bluetooth-enabled aftermarket alarm built by Acrisure Protection Group. It’s installed by dealers, primarily ...
- Russian State-Supported Cyber Actors Conduct Phishing Campaign Targeting Users of Zimbra Collaboration Suite
July 23, 2026
A group of Russian state-supported cyber actors has been targeting and compromising various Western government and commercial organizations using the Zimbra Collaboration Suite (ZCS) software since at least July 2025. The Russian state supported advanced persistent threat (APT) group’s activity is tracked in the cybersecurity community under several names (see Cybersecurity industry tracking), primarily as ...