Malicious NuGet Packages Unleash Time-Delayed Sabotage Threats

Researchers at Socket have uncovered a sophisticated supply-chain attack involving nine malicious NuGet packages that embed time-delayed sabotage code into legitimate .NET libraries. These packages, which were downloaded 9,488 times prior to the discovery, utilize hidden triggers to terminate host processes and, in one instance, corrupt write operations in industrial control systems.

Understanding the Attack

The malicious packages, released under the alias shanhai666 between 2023 and 2024, appear to provide legitimate functionality to gain the trust of developers and bypass initial scrutiny. Each package buries approximately 20 lines of harmful code within otherwise useful components. The attackers exploit C# extension methods, such as .Exec() for database operations and .BeginTran() for S7 PLC clients, ensuring that every database query or PLC operation automatically executes the injected sabotage routines.

The attack’s payload is timed with hardcoded or encrypted trigger dates, which are staggered, with some packages set to become active as late as 2027 or 2028. This strategy extends the attackers’ opportunity to compromise targets while remaining undetected. The most dangerous of these packages, Sharp7Extend, employs two sabotage mechanisms: an immediate probabilistic process termination on every PLC operation, and a delayed failure response that silently returns erroneous results for up to 80% of write attempts after a 30–90 minute grace period. This approach can lead to actuator non-responsiveness and failed safety engagements, mimicking hardware failures rather than revealing malicious intent.

Challenges in Detection

Several factors contribute to the difficulty in detecting these malicious packages. The legitimate code within them often passes functional testing and code reviews. Additionally, the technique known as typosquatting—where the names of the packages are similar to legitimate ones (e.g., Sharp7 vs. Sharp7Extend)—increases the likelihood of accidental installations in operational technology (OT) environments. The inclusion of genuine libraries further obscures red flags during integration testing.

Randomized and probabilistic activation of the malicious code makes systematic interference appear as random failures, complicating detection efforts. The significant delays between installation and activation hinder forensic investigations, often resulting in impacts being observed long after the initial installation. To further evade automated detection, the attacker varied author metadata and forged signature artifacts.

Building a Resilient Supply Chain

To counteract the risks posed by this NuGet campaign, organizations must take immediate and long-term steps to enhance their supply chain resilience. Here are several recommended actions:

– **Audit Dependencies**: Conduct an inventory of .NET packages and promptly remove or replace any of the nine identified malicious packages.
– **Enforce Dependency Hygiene**: Require verified publisher metadata, prohibit typosquatted names, and limit package sources to approved registries.
– **Integrate Scanning Protocols**: Implement Software Bill of Materials (SBOM) checks and static analysis in CI/CD pipelines to identify time-based logic, unusual extension methods, or obfuscated trigger code.
– **Monitor for Anomalies**: Set up alerts for date checks, randomized control flows, or unusual usage of Process.Kill() and extension methods within dependencies.
– **Validate ICS Integrity**: For industrial environments, ensure write-verification for PLC commands, establish baseline PLC success rates, and monitor for sudden drops in write confirmations.
– **Harden Supply Chain Policies**: Enforce least privilege for package installation, require thorough code reviews for third-party libraries, and apply strict change control for OT components.

By implementing these best practices, organizations can bolster their software supply chains and mitigate the risks associated with hidden malicious logic. This incident highlights how supply-chain attacks can weaponize trusted code and exploit time delays to inflict significant damage while remaining under the radar.