SignaCert was one of the first whitelisting products available, and it now boasts more than 1 billion predefined file signatures as part of its Global Trust Repository service. It also offers file authenticity ratings, wide platform support, extensibility through XML, and excellent documentation. SignaCert's significant weakness is that it does not natively block file executions -- the only product in InfoWorld's review that does not include this ability as a standard feature.
Instead of blocking unauthorized applications, SignaCert focuses on identifying deviations from trusted, predefined baselines of files and security configuration settings, specializing in midsize to large environments.
SignaCert Enterprise Trust Services is composed of the SignaCert Enterprise Trust Server appliance, a huge predefined file hash database (cloud service and local), and a client that works across more operating systems (including Windows, Linux, Mac OS X, and Solaris) than any of the reviewed competitors. SignaCert even claims to work across network device platforms, such as firewalls and routers, but I didn't test that functionality. It's also the only product to monitor security configuration settings, as well as registry and file objects.
SignaCert's nonpersistent Java client is the most customizable client in this review. You can tailor its behavior based on a variety of configuration settings (to cap CPU utilization, for example). You can even build your own client to support whatever you want as long as it confirms to SignaCert's XML formatting. SignaCert easily has the best documentation of any product in this review, including hundreds of pages on both client and server components.