I wouldn't worry bout the aliens, i don't think they will hurt you
		
		
	 
It seems despite my attempts to emphasize terrorism as my source of worry (facilitated by our porous borders) you are bent on making this an issue of immigration status.
Let me be clear, things like 
this are what get me.
From link: "As part of the GAO investigation, agents from the Office of Special Investigation (OSI), attempted to enter the United States at air, land, and sea ports of entry using fictitious identities and counterfeit documents. From October 2002 through January 2003, the agents entered various points of entry across the U.S. without ever having the authenticity of their counterfeit documents questions. In addition, on two occasions, no identification documents were requested upon entry."
I'd like to think preventing say, a dirty bomb from going off in our own country is more important than appealing to the sensitivities of those who used to be, or are related to,  people living in our country illegally, but hey, that's just me.  I hope this clears it up a little stunt.
From the 9/11 Commission:
Terrorist Travel
More than 500 million people annually cross U.S. borders at legal entry points, about 330 million of them noncitizens. Another 500,000 or more enter illegally without inspection across America's thousands of miles of land borders or remain in the country past the expiration of their permitted stay. The challenge for national security in an age of terrorism is to prevent the very few people who may pose overwhelming risks from entering or remaining in the United States undetected.31
In the decade before September 11, 2001, border security-encompassing travel, entry, and immigration-was not seen as a national security matter. Public figures voiced concern about the "war on drugs," the right level and kind of immigration, problems along the southwest border, migration crises originating in the Caribbean and elsewhere, or the growing criminal traffic in humans. The immigration system as a whole was widely viewed as increasingly dysfunctional and badly in need of reform. In national security circles, however, only smuggling of weapons of mass destruction carried weight, not the entry of terrorists who might use such weapons or the presence of associated foreign-born terrorists.
For terrorists, travel documents are as important as weapons. Terrorists must travel clandestinely to meet, train, plan, case targets, and gain access to attack. To them, international travel presents great danger, because they must surface to pass through regulated channels, present themselves to border security officials, or attempt to circumvent inspection points.
In their travels, terrorists use evasive methods, such as altered and counterfeit passports and visas, specific travel methods and routes, liaisons with corrupt government officials, human smuggling networks, supportive travel agencies, and immigration and identity fraud. These can sometimes be detected.
Before 9/11, no agency of the U.S. government systematically analyzed terrorists' travel strategies. Had they done so, they could have discovered the ways in which the terrorist predecessors to al Qaeda had been systematically but detectably exploiting weaknesses in our border security since the early 1990s.
We found that as many as 15 of the 19 hijackers were potentially vulnerable to interception by border authorities. Analyzing their characteristic travel documents and travel patterns could have allowed authorities to intercept 4 to 15 hijackers and more effective use of information available in U.S. government databases could have identified up to 3 hijackers.32
Looking back, we can also see that the routine operations of our immigration laws-that is, aspects of those laws not specifically aimed at protecting against terrorism-inevitably shaped al Qaeda's planning and opportunities. Because they were deemed not to be bona fide tourists or students as they claimed, five conspirators that we know of tried to get visas and failed, and one was denied entry by an inspector. We also found that had the immigration system set a higher bar for determining whether individuals are who or what they claim to be-and ensuring routine consequences for violations-it could potentially have excluded, removed, or come into further contact with several hijackers who did not appear to meet the terms for admitting short-term visitors.33
Our investigation showed that two systemic weaknesses came together in our border system's inability to contribute to an effective defense against the 9/11 attacks: a lack of well-developed counterterrorism measures as a part of border security and an immigration system not able to deliver on its basic commitments, much less support counterterrorism. 
These weaknesses have been reduced but are far from being overcome.
Recommendation: Targeting travel is at least as powerful a weapon against terrorists as targeting their money. The United States should combine terrorist travel intelligence, operations, and law enforcement in a strategy to intercept terrorists, find terrorist travel facilitators, and constrain terrorist mobility.