Fix Lockfile Integrity is a tool that reverts all sha1 integrity back to sha512 in lock files, supporting both package-lock.json and npm-shrinkwrap.json, working with lockfile versions 1 & 2, and can be configured to work on multiple paths for monorepo support. It only fixes packages from the npm registry by default, but this can be changed via a configuration file. The tool can be installed globally with 'npm install -g fix-lockfile-integrity' or run with npx, and usage involves checking a local folder for a lockfile and fixing any sha1 in it.