I heard about this on the news this morning and thought it was funny. Evidently, if you use keywords such as "collapse, outbreak, infection" in a Twitter tweet or Facebook comment, you'll pop up on the Department of Homeland Security (DHS) radar as a potential threat.
Source: Privacy and Security Fanatic: Privacy Advocates Sue DHS for Big Bro Fake 'Friends' Monitoring Social Media
Now, if you notice, the top 3 results all point to one thing: the Zombie Apocalypse.
There are two possible reasons for this:
Source: Privacy and Security Fanatic: Privacy Advocates Sue DHS for Big Bro Fake 'Friends' Monitoring Social Media
So, out of curiosity of what's really going on, I did a Google search for some of these terms.As set out in the Federal Register and Privacy Impact Assessments, the DHS's social media monitoring initiative would allow the agency to "establish [fictitious] usernames and passwords," to create covert social media profiles to spy on other users, deploy search tools, and record the online activity of particular users, based on the presence of such search terms as "illegal immigrants," "drill," "infection," "strain," "outbreak," "virus," "recovery," "deaths," collapse," "human to animal," and "Trojan."

Now, if you notice, the top 3 results all point to one thing: the Zombie Apocalypse.
There are two possible reasons for this:
- The Government is afraid of the public knowing of a naturally occurring Zombie existence
- The Government is afraid of the public knowing of a Zombie existence as a result of a military experiment gone wrong