Is there a way to find out who is buying or selling off large volume of stocks?
Is there a software/web program for this?
The SEC requires that Large Traders report trades to the SEC on Form 13H. A large trader is defined as someone who transacts:
2 million or more shares or $20 million in a NMS security during any one day
20 million shares or $200 million during any calendar month.
The SEC also requires that
"shareholders who acquire more than 5% of the outstanding shares of that class must file beneficial owner reports on Schedule 13D or 13G until their holdings drop below 5%."
"Section 16 of the Exchange Act applies to an SEC reporting company's directors and officers, as well as shareholders who own more than 10% of a class of the company's equity securities registered under the Exchange Act."
Other than SEC requirements, there is no public disclosure of who trades what each day.