Blocking search engines, charging the earth for internet, torturing activists to get their Facebook and Twitter passwords, passing laws that control what people can (and can't) talk about online.

These are just some of the ways in which nations from China to Iran, Cuba to Azerbaijan are preventing journalists, bloggers and activists from speaking out about human rights abuses.

In some countries, criticizing authorities online is so dangerous that, according to Reporters without Borders, 2011 was the deadliest year for online activists - with several 'netizens' killed in Bahrain, Mexico, India and Syria.

But journalists, bloggers and activists are coming up with new ways to by-pass internet controls and ensure their voices are heard by millions across the world.

"The opening of the digital space has allowed activists to support each other as they fight for human rights, freedom and justice around the world," said Widney Brown, Senior Director for International Law at Amnesty International.

"States are attacking online journalists and activists because they are realizing how these courageous individuals can effectively use the internet to challenge them. We must resist all efforts by governments to undermine freedom of expression."

Amnesty International has spoken to journalists and bloggers from Iran, Azerbaijan, Cuba and China who describe the daily challenges they face carrying out their work online.