A leaked forecast of the prospects for terrorism attacks in the United States over the next 5 years shows that the government appears to be most concerned about a biological attack that could devastate the economy:

Intelligence officials also predict that in the next five years, terrorists will try to conduct a destructive biological attack. Officials are concerned about the possibility of infections to thousands of U.S. citizens, overwhelming regional health care systems.

There could also be dire economic impacts caused by workers' illnesses and deaths. Officials are most concerned about biological agents stolen from labs or other storage facilities, such as anthrax.

"The threat of terrorism and the threat of extremist ideologies has not abated," Chertoff said in his year-end address on Dec. 18. "This threat has not evaporated, and we can't turn the page on it."

These high-consequence threats are not the only kind of challenges that will confront the U.S. over the next five years.

Terrorists will continue to try to evade U.S. border security measures and place operatives inside the mainland to carry out attacks, the 38-page assessment said. It also said that they may pose as refugees or asylum seekers or try to exploit foreign travel channels such as the visa waiver program, which allows citizens of 34 countries to enter the U.S. without visas.

Long waits for immigration and more restrictive European refugee and asylum programs will cause more foreigners to try to enter the U.S. illegally. Increasing numbers of Iraqis are expected to migrate to the U.S. in the next five years; and refugees from Somalia and Sudan could increase because of conflicts in those countries, the assessment said.

There is much to chew on in this report. It highlights the fact that at bottom, our intelligence on what terrorists are planning is really not very good. The report thinks a nuclear attack is "unlikely" but cautions against a bio attack. It says that Hezb'allah may attack targets inside the US if there is some kind of "triggering" event - presumably an attack on Iran's nuclear facilities. It also says that cyber attacks will become an increasing threat - but probably not from al-Qaeda.

And it warns of illegal border crossings by terrorists - something that DHS seems reluctant to do anything about at present.

Finally, the report says that there is a threat of increased competency of domestic terrorists like animal rights and enviro-wackos. This would make them more lethal although the threat of any mass casualty attack appears low.