1. A computer-implemented method for scanning user-generated web content for malicious behavior comprising: receiving user-generated web content, said user-generated web content for posting to a web content hosting system and being received from the user, the user intending that the content be posted to a website capable of receiving and serving user-generated web content; inputting said web content to a virtual machine; executing at least a portion of said web content by a web content scanning application, the web content scanning application itself executing within said virtual machine in a virtual environment, wherein executing the web content includes executing automatic execution code of the web content and executing one or more dynamic page actions present in the web content, the dynamic page actions exhaustively performing actions which would normally be performed by a human user, according to the web page content, including actively engaging one or more selection buttons by activating those one or more buttons virtually; monitoring said execution of said web content in said virtual environment for malicious behavior; determining whether said malicious behavior is detected based upon said monitoring; wherein upon a determination that said malicious behavior is detected, blocking posting of said web content to said web content hosting system; and wherein upon a determination that said malicious behavior is not detected, permitting posting of said web content to said web content hosting system.