Security Experts:

Thousands of VNC Instances Exposed to Internet as Attacks Increase

Dark web intelligence firm Cyble reports seeing an increase in cyberattacks targeting virtual network computing (VNC).

The VNC graphical desktop-sharing system relies on the Remote Frame Buffer (RFB) protocol to provide control of a remote machine over a network.

Exposing VNC to the internet has long been deemed a security risk, yet Cyble has identified over 8,000 internet-accessible VNC instances that have authentication disabled.

Cyble also warns of a spike in attacks targeting port 5900, the default port for VNC, noting that the Netherlands, Russia, and Ukraine have emerged as the top attacking countries.

Most of the exposed VNC instances, the threat intelligence firm says, are located in five countries: China, Sweden, the United States, Spain, and Brazil.

Some of the exposed VNCs belong to organizations in critical infrastructure sectors, including water treatment plants, manufacturers, and research facilities. Cyble says it was able to identify multiple human-machine interface (HMI) systems, SCADA systems, and workstations that are connected via VNC and internet-accessible.

Attackers able to compromise such systems may tamper with predefined settings, shut down industrial control systems (ICS), disrupt the supply chain and processes in the affected industries, or access sensitive data that can be used to further compromise ICS systems.

Exposing VNCs to the internet, Cyble notes, increases the likelihood of a cyberattack, including ransomware, data theft, and cyberespionage, all of which are typically preceded by an initial network compromise.

“Our investigation found that selling, buying, and distributing exposed assets connected via VNCs are frequently on cybercrime forums and markets,” Cyble notes.

While remote access to IT/OT infrastructure assets can prove handy, improperly implemented security measures could lead to highly impactful incidents and significant losses. Internet-exposed VNCs that lack authentication make it easy for attackers to access a victim’s network and create havoc.

“Readers should bear in mind that exposed VNCs from critical organizations put the national security, economy, energy, and transportation sectors at high risk of cyberattacks. It is advised that organizations using VNC and similar products should ensure that their ports and services are not exposed online and are appropriately secured,” Cyble concludes.

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