APT41 Exploits Google Calendar in Stealthy Cyberattack; Google Shuts It Down

Chinese state-backed threat actor APT41 has been discovered leveraging Google Calendar as a command-and-control (C2) channel in a sophisticated cyber campaign, according to Google’s Threat Intelligence Group (TIG). The team has since dismantled the infrastructure and implemented defenses to block similar future exploits.

The campaign began with a previously breached government website — though TIG didn’t disclose how it was compromised — which hosted a ZIP archive. This file was distributed to targets via phishing emails.

Once downloaded, the archive revealed three components: an executable file and a dynamic-link library (DLL) disguised as image files, and a Windows shortcut (LNK) masquerading as a PDF. When users attempted to open the phony PDF, the shortcut activated the DLL, which then decrypted and launched a third file containing the actual malware, dubbed ToughProgress.

Upon execution, ToughProgress connected to Google Calendar to retrieve its instructions, embedded within event descriptions or hidden calendar events. The malware then exfiltrated stolen data by creating a zero-minute calendar event on May 30, embedding the encrypted information within the event’s description field.

Google noted that the malware’s stealth — avo

[…]
Content was cut in order to protect the source.Please visit the source for the rest of the article.