The legislation is due to be signed into law by next month and the installation of software to block access to the sites will take more than three to six months.
Family Minister Ursula von der Leyen said areas in Britain, Italy and Scandinavian countries, which blocked access to child pornography websites several years ago, had been a model for Germany.
"If these countries can overcome any legal and technical issues and successfully fight child porn online, we can do the same in Germany," von der Leyen said.
All German Internet service providers will eventually have to adhere to the law. So far, the ISPs that have voluntarily agreed to sign a contract with the government and the Federal Crime Office cover 75 percent of the market.
Von der Leyen said the new measures could prevent about 80 percent of new consumers from gaining access to child pornography on the Internet.
Although the proposal has been welcomed by the federal telecommunications group Bitkom, the association's managing director Bernhard Rohleder warned against expecting the problems of child pornography to be solved.
Rohleder said that the proposed new law would have a limited effect because most child porn surfers would conceal their IP address and that many use peer-to-peer servers, which ISPs are powerless to control.
The ASACP's Tim Henning, who is the organization's technology and forensic research director, said he is encouraged that measures such as these have been implemented by countries in Europe.
"It will not solve the problem of child exploitation as there are methods to circumvent such technologies; however, it will certainly help to reduce child exploitation in these countries and filtering such content by ISPs is another tool that can be brought to bare in the fight to protect children,” Henning told XBIZ.
But, Henning said, "there is always a concern that a government may go too far in their filtering, which recently happened in Australia when the ISPs pulled out of the filtering test.”