BeEF is a powerful tool that exploits web and browser-based vulnerabilities such as client-side and XSS attacks. With BeEF you can put up a link that when a user clicks on it, it will hook that user's browsers into the frameworks server. From there you can run malware on the hooked browser's IP address and use it to invade another host on the same network, dispersing the malware effectively.
When you launch BeEF from Kali Linux, the default credentials for both the username and password is beef: