A Software Bill of Materials (software BOM) is a list of components in a piece of software. Software vendors often create products by assembling open source and commercial software components. The software BOM describes the components in a product. It is analogous to a list of ingredients on food packaging.
The concept of a BOM is well-established in traditional manufacturing as part of supply chain management. A manufacturer uses a BOM to track the parts it uses to create a product. If defects are later found in a specific part, the BOM makes it easy to locate affected products.
A software BOM is useful both to the builder (manufacturer) and the buyer (customer) of a software product. Builders often leverage available open source and third-party software components to create a product; a software BOM allows the builder to make sure those components are up to date and to respond quickly to new vulnerabilities. Buyers can use a software BOM to perform vulnerability or license analysis, both of which can be used to evaluate risk in a product.
Understanding the supply chain of software, obtaining a software BOM, and using it to analyze known vulnerabilities are crucial in managing risk.
The Cyber Supply Chain Management and Transparency Act of 2014 is pending US legislations that requires government agencies to obtain software BOMs for any new products they purchase. It also requires obtaining software BOMs for "any software, firmware, or product in use by the United States Government."