RTP: Audio and Video for the Internet

Most audiovisual content is passive : It comprises encoded data that is passed through a static decryption algorithm to produce the original content. With the exception of the issues due to nonuniform processing requirements noted earlier, such content is not dangerous.

There is, however, another class of content: that which contains executable code ”for example, Java applets or ECMAScript, which can be included with MPEG-4 streams. Such active content has the potential to execute arbitrary operations on the receiving system, unless carefully restricted.