Cabinet files are used to reduce file size and therefore the associated download time for Web content. This is essentially the same technology that has been used for years to compress software distributed on disks. Microsoft supplies a cabinet resource kit containing tools a developer can use to build .cab files. Cabinet files should be digitally signed. Signing Code received through the Internet lacks shrink-wrapped packaging and store clerks to vouch for its reliability.
Users are understandably wary when they're asked to download software from the Internet.
Digital signatures associate a software vendor's name with a given file, providing accountability for software developers. A signature reassures your users by creating a path from them to you if your software harms their systems. Internet Explorer's default security setting won't install a component that doesn't have a digital signature. For additional information about signing, see Signing and Checking Code with Authenticode . You can purchase digital signatures from a certificate authority, a company that validates your identity and issues a certificate for you.