Ultrahook (ultrahook.com) is a free, public-facing web service to enable webhooks. A webhook is an HTTP mechanism to allow third-parties to push content to your website. HTTP is inherently a pull technology--client requests, server responds. Ultrahook allows you to register a subdomain (e.g. mysubdomain.ultrahook.com) to accept HTTP POSTS which are then available to be pulled to your site or service from behind a firewall. This technology allows firewalls to be evaded, and is a security concern.

This SonicWALL signature identifies legitimate HTTP requests to Ultrahook.