The directive was issued yesterday by the Pakistan Telecommunication Authority (PTA), days after ban on the YouTube was lifted nearly after three years for carrying a blasphemous movie.
The move apparently follows a recent order by the Supreme Court wherein the telecom sector's regulatory body had been asked to "take remedial steps to quantify the nefarious phenomenon of obscenity and pornography that has an imminent role to corrupt and vitiate the youth of Pakistan".
PTA said it has decided to take pre-emptive measures to block such websites at the domain level to control dissemination of pornographic content through the internet as it provided ISPs with a list of 429,343 domains to be blocked on their respective networks.
The list provided by PTA was extensive and that they would face challenges, especially of time, while trying to block content, the report said.
Officials said that blocking websites at the domain level was a gigantic and costly exercise, since it would require changes in their systems and special equipment to block such a large number of websites not to mention a significant amount of man hours needed for this purpose.
However, they said that they had started work on the order since they were bound to abide by the law.