Agung Setyadi (left) and Agung Prabowo were arrested in 2006 and sentenced to prison for assisting in terrorist recruiting via the web. Indonesian extremists are increasingly using the Internet to spread their jihadist message. [Dadang Tri/Reuters]

Technological advancements have enabled terrorists to wage online propaganda campaigns through "hundreds" of jihad-themed websites, experts warn.

Terrorists' use of the Internet to spread their messages began in 2002 when Imam Samudra claimed responsibility for the Bali bombings via istimata.com, according to Noor Huda Ismail, executive director of the International Institute for Peace Building.

Ten years later, "there are hundreds of Internet sites" used to spread jihadist propaganda in Indonesia, run by groups and individuals, Noor Huda told Khabar Southeast Asia.

"There are also some individuals who manage several websites at one time," he said. "They usually use social media and/or free blog hosting such as Facebook or Blogpot to post information or ideas about jihad."

He said the Internet is one of the most effective ways for extremists to deliver their messages and find like-minded people.

Jakarta-based journalist Solahudin told Khabar that those websites contain information about jihad and Islam in general, and therefore tend to be attractive to their readers and followers.

One of the most popular topics on such sites, he said, is how to make a bomb from regular kitchen items.

"They can easily find out how to make bombs cheaply. They can purchase the ingredients such as match powder and also sugar without being noticed," he said. "That was actually what happened in Umar Bin Khattab boarding school in Bima, West Nusa Tenggara. They assembled a bomb with knowledge gained from the Internet."

The principal of the school was sentenced to 17 years in jail for preaching militant jihad and teaching his students to make bombs after a bomb exploded at the school on July 11, 2011, killing one person.

A Tangerang-based Islamic news portal, arrahmah.com, which provides information about jihad, published a letter on October 15th challenging Detachment 88 to an open fight.

According to the website, the letter was written by Abu Wardah, alias Santoso, the self-styled "Commander of Mujahideen in Eastern Indonesia," who is on the police most wanted list.

The letter, written in Indonesian, Arabic and English, was first released by al-busyro.org, a site which also contains updates on jihad preparation in Poso and can only be accessed by members.

"In order to be a member with those kinds of websites, a person will need a recommendation from another member. Other than that, the website opens registration during certain periods of time," Noor Huda said. "They do not want the information to be accessed freely."

In 2006, Detachment 88 arrested three men for helping create and maintain anshar.net on the order of Noordin M. Top, a bomb-maker killed in 2009, with the purpose of spreading jihad propaganda.

Abdul Aziz, a high school computer teacher who designed the site, was sentenced to 10 years in prison that same year. Agung Prabowo was given three years in 2007 for purchasing the domain name anshar.net and a hosting account, while Agung Setyadi was sentenced to six years for sending a laptop to Imam Samudra, who was jailed in Bali at the time.

The Ministry of Communication and Information claims it has been blocking many websites since electronic transaction and information regulations were set up in 2008.

"Unlike before, when we only blocked websites on request, we now have a system which automatically blocks any website that contains negative stuff, including pornography and radicalism," Gatot Dewa Broto, a spokesman for the ministry, told Khabar.

However, Gatot said, the ministry faces several obstacles in its efforts to block such websites, including limited bandwidth and human resources.

"If we block all the websites, it would hamper the public's Internet access and we'd rather avoid that," he said. "Secondly, we lack enough people who can keep monitoring the websites which contain negative material. It needs to be understood that we cannot just block any website based on like and dislike; it requires verification."

Indonesia has 220 Internet service providers, he said; monitoring them is a big job.

"With all of these problems, we keep trying to improve," he said.