There are 270,000 unauthorised Indians in the US - a 125 percent jump since 2000, the largest percentage increase of any nation with more than 100,000 illegal immigrants.Indians fastest-growing illegal immigrant group in US, The Economic Times, August 11 2009.
Many Indians get into the US with an H-1B Visa so they do not have to cross the border illegally. Indian illegal immigrants tend to have attained a higher level of education than other illegal immigrants in the US.
A bit over 10% of all Indian immigrants in the US are here illegally. Without H-1b visa expansion, it is likely that number would be significantly less. H-1b and related programs have created a community of co-nationals that can facilitate illegal immigration.