Win32/Winwebsec is a Trojan horse that is delivered via a fake YouTube link that entices users to download and install a rogue security Trojan. The Winwebsec page may contain a message like "I can't upload this to YouTube as it will get deleted. Click the link on the right to watch."
The malicious page will then prompt a user to download a fake video codec and install the Trojan horse. Once installed the user will see fake security and virus infection warnings.