What is the U.S. government doing to stop and prevent illegal immigration?

Obviously, no one knows exactly how many immigrants are in the United States illegally because they are undocumented and there is no way to keep track of them.  There are estimates though that in January of 2000 there were about 7 million illegal immigrants living in the United States.  Today, it is estimated there are over 10 million illegal immigrants. 

Since the attack on the United States on September 11, 2001, the issue of illegal immigration and tightening the security at all borders has gotten far more attention than at other time in U.S. history. There have been many proposals to stop illegal immigration including building a fence along the entire U.S./Mexico border.  There are groups of people who live along the U.S./Mexico border who take it upon themselves to patrol the border and to stop illegal immigrants from getting into the U.S. at deserted areas along the border where there are no U.S. immigration officials on post.