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:
- CIMB refutes claims of data breach involving 1.2 million records
March 4, 2026
CIMB Group Holdings Bhd has given assurance that claims circulating online about a data breach involving its customers are false and that customer data continues to be protected. The financial services provider said on social media platform X that its security teams have verified that all systems are secure and that customer data remains fully safeguarded. ...
- Europol, Microsoft, TrendAI and Collaborators Halt Tycoon 2FA Operations
March 4, 2026
Researchers from TrendAI have been tracking the infrastructure, as well as the campaigns and operator behaviors that can be linked to Tycoon 2FA to build a clearer picture of how its services was being used at scale. By November 2025, TrendAI had collected enough data to link the operation to an actor using the monikers “SaaadFridi” ...
- Google patches 129 Android security flaws — including a potentially dangerous Qualcomm zero-day
March 3, 2026
Google has released a new security update which fixed 129 vulnerabilities in the Android ecosystem, including 10 critical-severity bugs, and one high-severity issue apparently being exploited in the wild. In a security advisory, Google said that it fixed a buffer over-read vulnerability in the Graphics component (an open-source Qualcomm module). The bug, tracked as CVE-2026-21385, was ...
- Coruna: The Mysterious Journey of a Powerful iOS Exploit Kit
March 3, 2026
Google Threat Intelligence Group (GTIG) has identified a new and powerful exploit kit targeting Apple iPhone models running iOS version 13.0 (released in September 2019) up to version 17.2.1 (released in December 2023). The exploit kit, named “Coruna” by its developers, contained five full iOS exploit chains and a total of 23 exploits. The core technical ...
- Microsoft OAuth scams abuse redirects for malware delivery
March 3, 2026
Microsoft has warned organizations about ongoing OAuth abuse scams that use phishing emails and URL redirects to infect victims’ machines with malware and take over their devices. The phishing expedition targets government and public-sector organizations, according to a Monday report from Redmond’s security researchers. And while Microsoft Entra disabled the malicious OAuth applications, Microsoft’s infosec squad ...
- Hacktivists may have just cracked open ICE and exposed over 6,000 companies working with the DHS
March 3, 2026
A hacktivist group has claimed to have broken into systems belonging to the US Department of Homeland Security (DHS) and exposed sensitive files online. The group, with the self-awarded name “The Department of Peace”, stole data from the Office of Industry Partnership that contained contracts between DHS, Immigration and Customs Enforcement (ICE), and over 6,000 private ...