Supply Chain Attack

Attackers choose the weakest link instead of the best-defended door. A software vendor may have its build system tampered with, so a normal update carries hidden malicious code to thousands of customers. Other routes include poisoned open-source libraries, stolen credentials of a managed service provider, and altered hardware or firmware. Because the code often arrives signed and expected, ordinary perimeter controls rarely object. Defenders respond with supplier due diligence, software bills of materials (a list of every component inside a product), code-signing checks, limits on supplier access and monitoring for odd behaviour after updates. Practitioners meet the term in third-party risk reviews and incident post-mortems. Without supplier checks, one poisoned update reaches every customer on the same day.

A payroll software vendor's build server is breached, and a routine update is quietly altered. A mid-sized manufacturer installs it the next morning, as it does every month. Two weeks later its security team notices the payroll server contacting an unknown address. Investigators trace the connection back to the update and learn that around 1,500 other customers received the same file.