India and the United States have been steadily increasing their counter-terrorism intelligence cooperation over the last few years. The bloody Islamic terror attack in Mumbai last year, spurred the two countries to even greater cooperation.
The intelligence agencies of both nations have not always been so cozy. During the Cold War, India considered itself "non-aligned" (but pretty leftist and pro-Russia). When the Cold War ended, India continued to buy most of its imported weapons from Russia, but the leftists in government and military agencies were no longer as influential During the 1990s, India also instituted many economic reforms which got the economy going, and further discredited leftist politicians (including many communists). By the time September 11, 2001 came around, India (with a growing Islamic terrorism problem) and the United States began to work closely on military and intelligence issues.
Now it's reached the point where the CIA and FBI regularly work with their Indian counterparts. The U.S. still has an unofficial list of leftist Indian intelligence officials it asks to be kept out of the loop on some data sharing projects (as the Russians still have many friends within Indian intelligence). So far, all this sharing has gone well. The U.S. has a lot of Pakistani immigrants, and India has been useful in pointing which ones it knows to have an Islamic radical background. The U.S. has compiled a mountain of data on Islamic terrorism worldwide, and the Indians now have access to much of that.