Podjacking is hijacking as applied to podcasts. The first documented podjacking is written up here: Preventing and Surviving a Podjacking (By Erik Marcus)
Earlier today I wrote a bit about structured blogging and microformats. It strikes me that this podjacking incident is an example of the microformats the web2.0 wonks are talking about, and it's an example of the danger.
First, an RSS feed and a podcast are clearly an example of a "microformat". The purpose is to announce the existence of new postings, allowing others to keep up-to-date with a set of news. RSS is a simple XML format that's relatively easy to parse and is widely understood among webgeeks. Clearly RSS and podcasting are a hit on the Internet, making the Internet far more useful than in the days before this microformat existed.
For example it's now trivial to "broadcatch", a term that refers to tracking a broad set of information resources and picking out the ones of specific interest to a given set of people. That's all an RSS aggregator application does, is apply the broadcatch concept to news and blogging.
But there's also a danger. The RSS feed is a data file, and it's trivial to write software to play with it. What happened in this podjacking case was someone took an existing podcast/RSS feed, and wrote a script that republished a modified feed. The modified feed showed a different home page than the official one for the podcast. Further, the modified feed was indexed by several podcast search engines in place of the official podcast.
As a software author, I can see how it would be trivial to cook up the software to do this deed. It just means taking an existing podcast feed, modifying a few items, making a copy of the MP3 file, and republishing the feed as your own.
Web publishers should be aware this is possible. In the article linked above he includes some rational suggestions such as regularly looking for your feed in the popular search engines, and to attach appropriate copyright notices to your podcast feed. It becomes easier to legally "take care of" the podcaster if you've been diligent about establishing your copyright over the material you're providing.