Different from Phishing, Scarier than Malware: The Threat of Zero-Click Attacks

The Silent Cyber Threat

Welcome dear reader to today's conversation.

While it is true that cyber threats are evolving rapidly, it is even mind boggling that we are witnesses to the introduction of new and more sophisticated attack methods, that go beyond just clicking a link. One such emerging and highly dangerous threat is the zero-click attack—a highly targeted cyberattack often used in espionage campaigns that leaves minimal traces.

Most cyberattacks require some form of user interaction, such as clicking a link or opening a file. However, zero-click attacks bypass this requirement, infiltrating devices without any action from the victim. This makes them especially dangerous, as users remain unaware that their devices have been compromised.

Zero-click attacks exploit zero-day vulnerabilities, flaws that software vendors have not yet discovered or patched. Since no security updates exist to fix these vulnerabilities, affected users remain exposed to significant risks.

A Step-by-Step Breakdown

Zero-click attacks typically follow a structured approach, consisting of the following stages:

1. Finding and Exploiting Vulnerabilities

Attackers identify a zero-day vulnerability in a targeted application or operating system. Commonly exploited vulnerabilities include:

• Memory corruption bugs (e.g., buffer overflow, heap overflow, use-after-free, integer overflow)
• Logic flaws in data handling
• Sandbox escape vulnerabilities enabling privilege escalation

These vulnerabilities are cataloged under the Common Vulnerabilities and Exposures (CVE) database and tracked by organisations like MITRE under the Common Weakness Enumeration (CWE) framework.

2. Delivering the Malicious Payload

Once a vulnerability is identified, attackers craft a malicious payload and deliver it via channels that automatically process data, such as:

• Messaging apps (WhatsApp, iMessage, Telegram, Signal)
• VoIP calls (FaceTime, Skype, Zoom)
• Email attachments
• Multimedia files (GIFs, PDFs, images, videos, etc.)

Since applications process this data automatically, the exploit is triggered upon receipt.

3. Exploiting the Vulnerability and Executing Code

Upon processing, the malicious payload executes, allowing the attacker to:

• Bypass security restrictions (sandbox, ASLR, DEP, etc.)
• Access file systems, contacts, and stored data
• Escalate privileges to root/system level
• Establish persistence through backdoors or trojans

4. Deploying Spyware or Malware

Once the device is compromised, attackers can deploy:

• Spyware (e.g., Pegasus, FinSpy) to exfiltrate sensitive data
• Remote Access Trojans (RATs) for persistent control
• Rootkits to hide malicious activity

5. Erasing Evidence and Maintaining Stealth

To maintain stealth, attackers:

• Delete initial attack messages or notifications
• Modify or erase logs to remove traces of exploitation
• Prevent future security updates from patching the vulnerability

Notable Real-World Cases

Zero-click attacks are expensive and often target high-value individuals. Here are some notable real-life cases:

1. Pegasus Spyware (2016 - Ongoing)

• Delivered via zero-click iMessage exploits.
• Targeted journalists, activists, and political dissidents.
• Enabled full device surveillance, including microphone and camera access.
• Investigations revealed mass surveillance in multiple countries.

2. WhatsApp Zero-Click Vulnerability (May 2019)

• Exploited WhatsApp’s video call handling.
• Allowed attackers to install surveillance software upon receiving a video call.
• Affected 1,400 users across 20+ countries.

3. iOS 12 Zero-Click Exploit (2019)

• Exploited image processing vulnerabilities in iMessage.
• Allowed silent spyware installation upon receiving a malicious image.
• Primarily targeted journalists and dissidents.

4. Simjacker (2019)

• Targeted mobile phone users in Africa and the Middle East.
• Exploited SIM card vulnerabilities via SMS-based attacks.
• Enabled remote tracking, call interception, and location monitoring.

Protecting Against Zero-Click Attacks: Best Security Practices

Since zero-click attacks rely on undetected vulnerabilities, proactive defence is critical. Organisations and individuals should implement the following security measures:

1. Keep Software Updated

• Regular OS, firmware, and application updates.
• Immediate deployment of security patches.

2. Limit Exposure to Untrusted Data

• Disable auto-preview for emails and messages.
• Restrict applications from executing untrusted code.

3. Monitor for Unusual Activity

• Use Mobile Threat Defence (MTD) solutions.
• Enable logging and anomaly detection.

4. Use Sandboxing and Isolation Techniques

• Analyse incoming messages in virtualised environments.
• Implement AppArmor/SELinux policies for additional security layers.

5. Strengthen Network Security & Endpoint Protection

• Implement firewall rules to block connections to malicious servers.
• Use DNS filtering to prevent malware downloads.

6. Stay Informed and Train Users

• Educate users on spyware risks and zero-click attack methods.
• Conduct Red Team exercises to simulate real-world attack scenarios.

The Need for Vigilance

Zero-click attacks represent a growing cybersecurity challenge due to their stealth and sophistication. By exploiting zero-day vulnerabilities, attackers can infiltrate devices without user interaction, making detection and mitigation difficult. Organizations and individuals must adopt proactive security measures such as patch management, behavioral monitoring, and application hardening to protect against these evolving threats.

Till next time, stay alert!

References

MITRE ATT&CK Framework - attack.mitre.org, CWE Mitre - cwe.mitre.org, CVE Details - cvedetails.com, Google Project Zero - googleprojectzero.blogspot.com, Citizen Lab (Pegasus Spyware Research) - citizenlab.ca, Check Point Research - research.checkpoint.com, Microsoft Security Research - microsoft.com/security/blog