2013 U.S. Homeland Security Budget
Among other findings in this CBO report:
Funding for homeland security has dropped somewhat from its 2009 peak of $76 billion, in inflation-adjusted terms; funding for 2012 totaled $68 billion. Nevertheless, the nation is now spending substantially more than what it spent on homeland security in 2001.
Note that this is just direct spending on homeland security. This does not include DoD spending—which would include the costs of the wars in Iraq and Afghanistan—and Department of Justice spending. John Mueller estimates that we have spent $1.1 trillion over the ten years between 2002 and 2011.