Google Calendar Under Threat: GCR Tool Uses It for Command-and-Control Operations
Google has issued a warning regarding the emergence of a novel threat, GCR (Google Calendar RAT), which employs Google Calendar for clandestine command-and-control (C2) operations. Although the tool itself hasn’t been spotted in actual cyberattacks, as the 8th Threat Horizons report showed, the sharing of its public proof-of-concept (PoC) on underground forums has raised concerns among security experts.
Google Calendar as a Covert Channel for Cyberattacks
The GCR tool, developed by an individual known by the online alias MrSaighnal, utilizes Google Calendar Events to create a covert channel for cybercriminals. It accomplishes this by manipulating event descriptions within Google Calendar, effectively turning the widely used application into a command-and-control infrastructure. What’s notable about this approach is that the target device connects directly to Google’s infrastructure, providing a certain level of concealment.
A Cloak of Legitimacy
One of the most concerning aspects of GCR is that it operates exclusively on legitimate infrastructure, which poses a significant challenge for defenders. Since the tool functions within the confines of a widely trusted service like Google Calendar, it becomes incredibly difficult to detect any suspicious activity. This makes it easier for threat actors to operate stealthily and evade traditional security measures.
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A Growing Trend: Abusing Cloud Services
This development highlights a growing trend in the realm of cyber threats – the exploitation of cloud services as a means of infiltrating victim environments while remaining inconspicuous. Threat actors are increasingly turning to these services to conduct their operations, leveraging the trust users place in them to navigate under the radar. This modus operandi is exemplified by GCR’s use of Google Calendar.
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Further Insights from Google’s Threat Analysis Group
Google’s Threat Analysis Group has been actively monitoring the threat landscape and has identified other instances of threat actors exploiting cloud services. An example involves an Iranian nation-state actor using macro-laced documents to compromise users with a .NET backdoor known as BANANAMAIL.
This malware utilizes email for command-and-control operations and uses IMAP to connect to an attacker-controlled webmail account for communication. In response, Google has taken action to disable the attacker-controlled Gmail accounts used by this malware.
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Source: thehackernews.com
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