What attackers do. Attackers tamper with software dependencies and development tools, such as open source packages, build tools or code editor plugins, so that the compromise spreads into the software built with them. This serves Initial Access.
How to defend. Pin dependency versions, use lock files and internal package mirrors, and scan dependencies for known malicious packages. Protect developer workstations and build systems, require code review for dependency changes and keep a software bill of materials. Run builds in isolated, monitored environments with restricted network access.
Signs to look for. Look for new or renamed packages similar to popular ones, install scripts making network connections, unexpected changes in package maintainers and build systems contacting unknown domains. A common gap is developer machines having broad access with little monitoring.