TEHRAN -- Iran's powerful Ministry of Information and Communications Technology has blocked the most popular software used by millions of Iranians to bypass an elaborate official Internet filtering system, stepping up a campaign to gain more control over the way Iranians use the Internet.
As of Thursday, a collection of illegal virtual private networks, or VPNs, was successfully closed off by the ministry, making visits to Web sites deemed immoral or politically dangerous -- like Facebook and Whitehouse.gov -- nearly impossible.
Popular mobile applications like Viber, for free phone calls, and WhatsApp, for free text messaging service, have also been experiencing problems.
People trying to visit illegal Web sites are being directed to a page on which users are encouraged to report illegal use of the Internet. This page, Peyvandha.ir, also explains in Persian that Web sites that promote "debauchery, boozing, pornography, the sharing of pictures and advocating ideas against religion" are forbidden.
The VPNs helped users to go online through foreign-based servers and visit Web sites anonymously and unrestricted. While illegal in Iran, the software, which requires user names and passwords, has been widely available in the country.
Industry insiders say that hardware to block the VPNs was installed in the Ministry of Information and Communication Technology and its regional centers several months ago, and that after several test periods Iran now has the ability to control the software when used in Iran.
In recent years, Iran's leaders have been labeling foreign Web sites and social media networks with increasing frequency as tools operated by foreign intelligence agencies. While several Iranian political figures, among them the supreme leader, Ayatollah Ali Khamenei, have Facebook pages, the authorities say the pages were created by fans.
While the Ministry of Information and Communication Technology executes Iran's elaborate filtering policies, the National Center for Cyberspace, established a year ago as the Supreme Council for Cyberspace, decides which Web sites should be blocked.
Mehdi Akhavan Abadi, the center's secretary, said last month that a new "smart filtering" system would be introduced within 90 days that would block only indecent or otherwise sensitive parts of a Web site, the semiofficial Mehr news agency reported.
Recognizing, however, that unfettered access to the Internet is essential for doing business, conducting research and other everyday activities, the National Center for Cyberspace last month started offering its own, state-controlled VPN software with the proviso that users promise not to visit sites deemed illegal.
Eliminating the informal VPNs and replacing them with a government-run network is not an idle exercise, as one employee of the Ministry of Information and Communication Technology explained.
"They could not see what people were doing while they used illegal VPNs," said Hassan, 44, who did not want his family name mentioned. "They used to be anonymous, but anyone who uses their software will have every click tracked."
This article originally appeared in The New York Times.