SideWinder Launches ClickOnce-Based Attack Chain on Diplomats

A new campaign orchestrated by the threat actor known as SideWinder has emerged, targeting a European embassy in New Delhi and multiple organizations across Sri Lanka, Pakistan, and Bangladesh. This operation, which began in September 2025, marks a significant evolution in SideWinder’s tactics, techniques, and procedures (TTPs), particularly through the use of a novel PDF and ClickOnce-based attack chain. The adoption of this method indicates a shift in how this group conducts cyber operations, emphasizing the need for heightened vigilance in network security and data protection.

Details of the ClickOnce-Based Attack

The ClickOnce-based attack chain employed by SideWinder is noteworthy for its sophisticated approach to infiltration. ClickOnce is a Microsoft technology that allows for the deployment of Windows applications via a web browser. By leveraging this technology, SideWinder can create a seemingly legitimate environment for users, making it easier to execute malicious payloads without raising immediate suspicion. This method involves crafting infected PDF documents that, when interacted with, trigger the ClickOnce application to install malware on the victim’s system.

The implications of such an attack are severe, particularly for diplomats and organizations involved in sensitive communications and operations. The use of PDF files as a delivery mechanism is particularly concerning due to the widespread use of PDF readers and the general trust users place in such documents. As a result, the likelihood of successful infection increases, allowing attackers to gain unauthorized access to confidential data and communications.

Risks and Implications for Users

The risks associated with this new ClickOnce-based attack chain extend beyond immediate data breaches. Cybersecurity vulnerabilities like those exploited by SideWinder can compromise user privacy and system integrity, leading to potential espionage, data theft, and disruption of critical services. For users, especially those in diplomatic roles, the fallout from such attacks can include loss of sensitive information, reputational damage, and strained international relations.

Moreover, the targeted nature of this campaign highlights the importance of threat intelligence in identifying and mitigating risks. Organizations must remain vigilant and proactive in their cybersecurity measures, particularly as attackers adopt more sophisticated methods. The potential for widespread impact necessitates a comprehensive approach to network security, ensuring that all systems are adequately protected against emerging threats.

Context

This incident is part of a broader trend in which cybercriminals increasingly target high-profile organizations and individuals, particularly in politically sensitive regions. The evolution of attack methods, such as the transition to ClickOnce-based techniques, reflects the ongoing arms race between attackers and defenders in the cybersecurity landscape. As threat actors continue to innovate, organizations must adapt their strategies to safeguard against new and evolving threats.

What to do

To mitigate the risks associated with the SideWinder ClickOnce-based attack, organizations and individuals should take the following steps:

Update all affected software to the latest versions immediately to patch known vulnerabilities.
Enable automatic updates where possible to ensure timely protection against emerging threats.
Monitor security advisories from affected vendors for updates and guidance.
Use a VPN service like ProtonVPN to protect your internet traffic and enhance privacy.
Consider additional security measures like multi-factor authentication to further secure sensitive accounts.
Alternatively, use a reliable VPN service such as Surfshark for an added layer of security.