Hordes of Indian and Chinese students fall hook, line and sinker for fake U.S. colleges which have websites with smiling professors, enthusiastic video testimonials, happy students in caps and gowns and promised leafy campuses in San Francisco Bay Area suburbs.

"I paid $4,500 for my first semester at Tri-Valley University, but never received an assignment. I wasn't learning anything and was trying to transfer to another school when Tri-Valley got raided," said B.V Subbarao.

"It was the most terrifying experience in my life. Immigration officials questioned my motives for being in the U.S," added Subbarao.

Tri-Valley University, housed in a single building in Pleasanton, California, was shut down on January 19, 2011 and labeled a "sham university" by immigration officials.

When the school was shut down, over 1,000 foreign students, hundreds of them from India and China, were stripped of their student status and deported. They lost money which they had paid upfront in tuition fees and had their American dreams smashed. The Tri-Valley case sparked protests in India as U.S. authorities clamped ankle monitors on hapless students from India who were cheated out of an education. It is one of the largest U.S. school fraud scams to date. The school's founder and president, Susan Xiao-Ping Su, used over $5.6 million she made in the scam to buy real estate, Mercedes Benz cars and multiple homes.

At least a dozen schools have been shut down or raided by U.S. federal authorities in recent years over allegations of visa fraud. These "diploma mills" admit foreign students but offer little or no instruction. In March this year, federal agents cracked down on Prodee University, located in Los Angeles. It is affiliated with three other schools: Walter Jay M.D. Institute and American College of Forensic Studies in Los Angeles and Likie Fashion and Technology College in nearby Alhambra.

“People think foreign students come to New York University and Harvard. We have a lot of mom-and-pop schools,” said Rachel Canty, deputy director of Immigration and Customs Enforcement's (ICE's) student exchange and visitor program, which certifies schools that enroll foreign students.

“We have been working to fix vulnerabilities,” she added.

ICE has begun deploying field reps to foster compliance with regulations; a compliance unit makes surprise visits to schools and identifies suspicious activity at schools.

On Sunday night, Air India played unlikely hero in stopping 19 students from Hyderabad from boarding a flight to San Francisco as they risked being deported when they arrived on the West Coast to enroll in two 'blacklisted' U.S Bay Area schools. Air India says it received a heads-up on December 19 from the U.S. Customs and Border Protection agency about the Silicon Valley University, in San Jose and North Western Polytechnic College, in Fremont.

However, the two universities said they have not been blacklisted and the increased vigil and questioning of Indian students at the port of entry are in view of the recent terrorist attacks on the West Coast.

Although both these Bay Area schools have presentable physical campuses, like Tri-Valley, these two universities have students mostly from India (Andhra and Telangana) and faculty from China and Taiwan. Jerry Shiao, president and academic dean of Silicon Valley University, did not return calls from this reporter.

While anyone can fall prey to a U.S. college scam, foreign students and first generation college students can be especially vulnerable to degree mills, say experts. "If you don’t know what you don’t know, it can seem like a really intricate maze," quipped one educationist.

These are warning signs that a school may not be legit:

1. Shortcut to Optional Practical Training
   Sham colleges dubiously facilitate shortcuts to Optional Practical Training (OPT) and Curricular Practical Training (CPT), the two routes to employment at the end of the college degree, from the first day of enrollment.
   
   Typically, in well-regarded universities, all students must be enrolled as full-time students for at least a year before becoming a part of CPT or OPT programs. For the hundreds of thousands of Indian students who have eventually become U.S. citizens, OPT and CPT are the first steps to employment-based H-1B visas, Green Card, and citizenship, in that order.
   
   Here is a notorious case of OPT misuse. College Prep Academy in Duluth, Georgia, president Dong Seok Yi conspired to enroll some women with the understanding they would not attend classes, but exploit the OPT program to work at bars. He was convicted of immigration document fraud and sentenced last year to 21 months in prison.
    
2. Fuzzy Accreditation
   Do your homework to ensure that the information you are gleaning from a website is trustworthy. When in doubt about a college determine if the institution is properly accredited.
   
   To make sure the accrediting organization is legitimate, students should make sure it is recognized by the U.S Department of Education. To be certified by immigration officials to accept foreign students, schools must be accredited by a Department of Education-approved organization like the Virginia-based Accrediting Council for Independent Colleges and Schools or have their courses accepted by at least three accredited schools.
   
   If you are unsure about a school claiming accreditation, you can always contact the accrediting agency and simply ask. The accrediting agencies get a lot of calls and are happy telling students exactly where things stand with U.S. schools.
    
3. Name Seems Weirdly Familiar
   Don't put it past a fake school to steal a renowned name and tweak it just a little bit and even conjure an illustrious faculty. If you comes across, for example, a professor Drew Gilpin Faust at a school with a name like Harvard Technological University, you should definitely sniff a rat.
    
4. No​ Student Services
   In most American colleges students are spoiled for support and websites offer a diverse range of programs, services and resources to help students. If prospective students don't see evidence of those resources, or if they can't speak to staff members, then they should be very suspicious.
   
   As one academic put it: "Poke around a little bit on the website to ensure that it isn’t just a movie set where it's just the front and that’s it."
    
5. Avoid Degree Mills like the Plague
   If your academic profile is sadly below average and you have applied to schools that are below average, then you could run into trouble if ICE decides to raid and shutdown your school for some infraction. Last year alone, the Counterterrorism and Criminal Exploitation Unit of U.S. Immigration and Customs Enforcement's Homeland Security Investigations office flagged about 150 of the roughly 9,000 schools certified to accept foreign students for investigation as potential visa mills.
   
   Most aspiring foreign students try and get into the top 50 U.S. schools, which have stringent qualifying standards, including exams such as GRE and GMAT, besides TOEFL. The process involves gaining admission on the basis of test scores, in lieu of which the university, if it is accredited and complaint with U.S. rules, sends an I-20 document to the accepted student, which he or she presents to the U.S. embassy in the home country to get an F-1 student visa.
   
   The tier three schools can send you an I-20 if they have accreditation but there is always the danger of them getting raided and shut down by U.S. federal investigators and becoming blacklisted. This will leave you in a limbo with your money washed down the drain.
    
6. Tune into Chat Rooms
   Most often students can clearly see the writing on the wall in Internet forums if they bother to trawl these chat rooms. In an exchange that began in April 2010, students, both prospective and inquiring, and those already committed to Tri-Valley University, slugged it out online. "Has any one got any experience with Tri-Valley University?" inquired one student. He had heard they offer "hassle free admission, GRE, GMAT not mandatory. No tests, no mandatory classes, a perfect way to bypass the visa process!"
   
   In no time, there were red flags. "Tri-Valley is NOT accredited, so you can NOT get a degree from them. Any 'degree' they issue is worthless," wrote one forum member.
   
   Your antenna should decode this sort of chatter to clearly mean nothing but bad news.
   
   The U.S. higher education system is considered the gold standard in education and the scams have the potential to hurt legions of foreign students who gravitate towards America every year.
   
   Nearly a million international students are studying at colleges across America. India is the second-largest country of origin for international students in the U.S. after China which sends 304,040 students. From 102,673 students enrolled in U.S. institutions in 2013-14, the number rose to 132,888 in 2014-15, according to the annual Open Doors survey.
   
   In recent years, U.S. authorities have raided schools in Virginia, New Jersey and California.
    

Uttara Choudhury is Editor, North America for TV 18’s Firstpost news site and a writer for Forbes India. In 1997, she went on the British Chevening Scholarship to study Journalism in the University of Westminster, in London.