Open source malware surges 140% in Q3 2025: Report

A new set of data from the Open Source Malware Index Q3 2025 reveals a major escalation in software supply chain attacks. Security analysts at Sonatype reported detecting 34,319 new malicious open source packages in the quarter, marking a 140% increase compared to the previous quarter.

The Q3 2025 analysis confirms that cybercriminals increasingly focus on intelligence gathering and establishing long-term, covert access within enterprise networks.

The distribution of new threats highlights this shift:

• Data Exfiltration: Malware designed to steal sensitive data accounted for 37% of all malicious packages detected. This tactic targets credentials, intellectual property, and proprietary code.
• Droppers: Packages used to deliver multi-stage payloads saw a massive rise, skyrocketing by 2,887% to represent 38% of total threats. This points to attackers building modular, persistent attack chains.
• Backdoors: Packages containing backdoor functionality grew by 143%, indicating a steady focus on maintaining long-term, secret access to compromised environments.
• Cryptominers Decline: Low-reward exploits like cryptominers fell to only 4% of threats, showing attackers prefer advanced, financially motivated techniques.

The data indicates that low-severity malware detections are declining as adversaries concentrate efforts on attacks that maximise disruption and data theft.

Developers become the primary target

The report clearly identifies developers as the new security perimeter. Attackers exploit the open nature of ecosystems like npm, PyPl, Maven Central and Hugging Face by creating malicious components that mimic legitimate dependencies.

These attacks rely on common developer errors like typosquatting, dependency confusion and account takeovers. Once compromised, these malicious components can steal credentials or inject backdoors into crucial CI/CD (Continuous Integration/ Continuous Delivery) pipelines.

Incidents impacting billions of downloads

The quarter saw two major incidents that demonstrate the dangers of supply chain compromise.

The Chalk and Debug Hijacking where attackers successfully phished the maintainer of several highly popular npm packages. These packages collectively see over 2 billion weekly downloads. The resulting injection of hijacked versions into legitimate projects showed how social engineering remains an effective tool for large-scale compromise.

The next incident was the Shai-Hulud Worm, which introduced a self-replicating worm targeting the npm ecosystem. The autonomous malware quickly compromised more than 500 npm components in days, showing the potential speed and scale of self-propagating threats.

Enterprise and government under fire

Open source attacks have severe implications for the business world and public sector infrastructure.

In Q3 financial services organisations faced the highest number of blocked attacks (47%), followed by business services (14%), and energy and utilities (8%).

Attacks bloacked against Federal organisations increased by 218% compared to Q1, showing adversaries are increasingly targeting public sector systems.

As the total number of malicious packages exceeds 877,000, enterprise security programs must adapt. Relying on perimeter defense is insufficient. Organisations need continuous vigilance and automated processes to secure the foundation of their software.

To protect against this maturing threat, organizations need to:

1. Automate the early-stage blocking of threats within development environments.
2. Continuously monitor dependencies for known and emerging vulnerabilities.
3. Implement cryptographic checks to verify the integrity and origin of all components.
4. Provide training to developers on recognizing and avoiding open source risks.