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:
- UK MoD says no data leaked to China via drone vulnerability
August 10, 2026
Britain’s Ministry of Defence said on Monday that there is no evidence that military data was compromised after a cyber vulnerability was discovered in Royal Navy drones. The issue was identified during routine cybersecurity testing, the ministry said, adding that it continues to conduct security checks across its equipment and systems. Read more… Source: EUROACTIV Sign up for the ...
- Top US hedge funds targeted by major vishing campaign
August 9, 2026
Some of the biggest US hedge funds and law firms have been targeted by a highly sophisticated data breach and extortion campaign, conducted by a group of criminals previously known as BlackFile, experts have warned. BlackFile (or Redact, as the group is now calling itself) has a relatively simple modus operandi, also used by ShinyHunters – ...
- Ransomware gangs skip the CEO, head straight for the 40-something IT manager
August 9, 2026
Turns out the fastest way to get a company to consider paying a ransom isn’t calling the CEO – it’s targeting the 46-year-old IT manager. That’s according to Zscaler, whose ThreatLabz researchers tracked 351 victims across 334 organizations caught up in a single ransomware campaign over the course of a month. The data suggests today’s ransomware crews have ...
- Security researchers scanned the Polish web and found courts, hospitals, and airports at risk of hacks
August 7, 2026
Two Polish security researchers wanted to find out how vulnerable their country’s internet was to potential cyberattacks and quickly found that thousands of public agencies and websites were at risk of being hacked. At the Def Con cybersecurity conference in Las Vegas on Friday, security researchers Robert Kruczek and Kamil Szczurowski said they wanted to understand ...
- Swiss government says SharePoint-linked data breach affected hundreds of accounts
August 7, 2026
Cybercriminals broke into the IT network of the Swiss government and stole data from roughly 200 accounts. As a result, the Swiss government disconnected some of its servers from the wider internet and launched an investigation. In an announcement, the Swiss government said that on July 28 2026 its security specialists noticed “abnormalities” in the Federal ...
- Buggy microcontrollers making up some of the world’s most important servers can be easily backdoored
August 6, 2026
Security researchers have discovered more than a dozen new vulnerabilities in Baseboard management controllers (BMC), hardware components found in thousands of the world’s most popular enterprise servers. BMCs are specialized chips built into servers that allow administrators to remotely monitor and manage hardware regardless of the operating system, and even when the hardware is turned off. They provide ...