Manning was speaking at the C2 business event which was held in Montreal, when she voiced her concerns regarding mass surveillance, and called on programmers and computer scientist to examine the ethical implications of some of the technologies it is developing.
Manning said, "Ten years ago, I was working in military intelligence and I could feel the power, and could see how technology is implemented. I'm stunned by the dramatic change in policing style, and how aggressive government surveillance has become. It's getting worse all over, but particularly in the United States."
The former US army intelligence analyst was jailed for 35 years for leaking classified information. She was sentenced in 2013 after being found guilty of leaking 700,000 classified documents which were related to the wars in Iraq and Afghanistan.
In addition to this, Manning urged programmers and computer scientists working on artificial intelligence and machine learning "to consider the ethical implications of the technology that they are building and developing.
The revelations made by Manning, who is transgender and was then known as Bradley Manning has made her one of the world's most famous whistleblowers and exposed covered-up misdeeds and possible crimes committed by US troops and allies.
Her actions made Manning a hero to anti-war and anti-secrecy activists, but US establishment figures branded her a traitor. Then-president Barack Obama commuted her sentence - leading to her eventual release in May 2017.