When the Sept 11 attacks occurred, Dr Shafiq Rahman was a mass communications doctoral student at Southern Illinois University in the United States. He had arrived two years earlier from Bangladesh.

"At that time, I was not scared at all," he said. "I thought, okay, this thing happened. Why do I have to be scared? I'm not part of it."

But soon afterwards, some of his professors and co-students asked if he needed a ride home. People he knew began calling, offering to go grocery shopping with him.

"All of a sudden, I was thinking, 'What is going on? Am I in danger?' " Dr Rahman, 53, now the department chair of communications studies at California State University, San Bernardino, told The Straits Times. "That was the beginning of the uneasy feeling."

It is a feeling Muslims in the US and many other parts of the world know only too well, having been subjected to hostility ranging from unfriendly stares to institutional discrimination. The resultant Islamophobia from the acts of terror perpetrated by 19 hijackers on Sept 11 has been apparent from time to time.

In 2016, when then US presidential candidate Donald Trump told CNN "I think Islam hates us", it demoralised Dr Rahman's daughter who was about to start college.

He remembers her telling him she did not want to stay on in a country where she is constantly reminded that Muslims do not belong.

Malaysian IT specialist Siti Fairuz Umoh, 39, who claimed she was religiously profiled on a few occasions soon after arriving in the US, said anti-Muslim sentiment and harassment escalated after Sept 11.

"It changed the world so much," she said, adding that she has never been afraid to stand up for herself. "But then again, this is America. We still have to be careful and responsible for our actions to avoid any conflict."

The post-9/11 climate also brought on discrimination that Muslims faced in travelling to the US and other countries, contributing to a sense of mistrust that still lingers. It has not spared even newsmakers, including Bollywood actor Shah Rukh Khan, who was detained thrice at US airports between 2009 and 2016.

In Indonesia, instances of alleged discrimination faced by those with Arabic-sounding names have been reported. Indonesian travel writer Muhammad Arif Rahman, 35, spent additional hours in the immigration office upon arrival at a New York airport. He had flown to the US at the invitation of heavy machinery equipment company Caterpillar after winning a blogging competition.

"After 9/11, the US has tightened restrictions on people coming to their country - with visitors bearing Muslim names often getting extra checks - because the terrorists claimed they represented Islam," he wrote in a 2014 blog.

"I think 9/11 changed the global depiction of Muslims. The idea of a Muslim as the terrorist was solidified after 9/11," Ms Saba Naqvi, a senior Indian journalist and author, told ST. "It just became cast in stone."

With their faith and community tarnished by the attacks, many Muslims have since reasserted their identity and countered misinformation through conversations. A more nuanced understanding of Muslims' diversity and Islam has emerged through a resurgence of organisations focusing on improving interfaith relations as well as individuals who have become foot soldiers for the cause.

Dr Nuurrianti Jalli, 35, an assistant professor of communication studies at Northern State University in South Dakota, for instance, actively promotes diversity and inter-cultural understanding in her class, besides advocating for justice, mutual respect and peace.

"All of these values are reflected through the syllabuses I develop for my courses," she said, adding that she hopes people will understand that actions by a certain group of extremists do not represent the whole religion.

Dr Rahman feels inter-community relations have improved, but argues they are still at the crossroads, with key challenges such as biased understanding of globalisation's impact, extreme nationalist discourse and Internet-driven misinformation.

But he feels the youth today are more open-minded and an emerging "sense of social and environmental justice" around the world gives him hope for a better future.

• With inputs from Nadirah H. Rodzi in Kuala Lumpur and Wahyudi Soeriaatmadja in Jakarta