Social Security to illegal immigrants

It seems the government sees fit to give an already unstable system a little more drain. We have illegal immigrants who now qualify for Social Security benefits after only 18 months as opposed to U.S. citizens who qualify after 10 years of employment. One pro immigrant benefits position is that 2/3 of illegal immigrants pay taxes and therefore should be entitled to benefits. My feeling is, yes that's true. Two thirds of the illegal immigrants they "know" about probably do. It's the 80% they don't have tabs on that concern me. Specifically due to the drain they put on society in regards to border towns, hospitals, and government assistance. Second, why are illegal immigrants afforded more from our government than citizens? What are your thoughts regarding this issue?