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:
- New phishing campaign hits LastPass, Bitwarden users
July 15, 2026
Criminals have been found impersonating popular password managers LastPass and Bitwarden online in an attempt to trick users into sharing their login credentials, and thus access to a treasure trove of passwords and other secrets. LastPass recently issued a warning to its customers, raising awareness of the ongoing phishing campaign. However the scam also now seems to ...
- Top AI tools such as OpenClaw and Github Copilot can be hijacked to create new massive botnets
July 15, 2026
Your favorite AI service could be subverted to deploy code that turns your phone or PC into a botnet, according to researchers at Intuit, Technion, and Tel Aviv University. The technique has been given the name HalluSquatting, a portmanteau of adversarial hallucination squatting, and is similar to typosquatting in that it relies on a mistake in ...
- Warning: Scammers are using FaceTime to empty bank accounts
July 14, 2026
Apple is urging users to treat any suspicious FaceTime call or message as untrusted, especially if it involves payments, refunds, password resets, or requests for personal information. This warning appears in a broader Apple support article about scams that target iPhone and iPad users through social engineering. Apple says attackers may contact people by phone calls, FaceTime, text ...
- Microsoft tops last month’s record with 622 Patch Tuesday CVEs
July 14, 2026
Remember last month when we were awed by Microsoft’s record-setting Patch Tuesday that addressed 206 CVEs? That was a quaint era compared to this month: Redmond just rolled out patches for 622 CVEs specific to its products, slightly more than tripling last month’s all-time high. Redmond’s Patch Tuesday release is once again one for the record books, with everything under ...
- Ghostcommit attack hides malicious AI instructions in images
July 13, 2026
Ghostcommit is a proof of concept that shows how AI assistants used to review software code can be tricked by hidden instructions embedded in images. The academic ASSET Research Group showed that an attacker can place instructions inside an image file, point to it in an AGENTS.md file, and get an AI coding agent to follow those instructions during a ...
- EU-UK sanctions target Russia over Europe-wide ‘vast cyber campaign’
July 13, 2026
The European Union and the UK have announced coordinated sanctions against Russia after accusing Moscow’s FSB intelligence agency of carrying out a cyber attack in December targeting Poland’s energy grid and orchestrating a wider campaign of digital sabotage across Europe. The joint measures focus on individuals and organisations linked to Russia’s security services, with the EU ...