There’s been ample video proof that Syrian rebels have received some Chinese FN-6 shoulder fired anti-aircraft missiles. There are a few dozen FN-6s (which have a distinctive shape to them) seen used by rebels in the last few months. While China has some missiles similar to the U.S. Stinger, these are not exported. The FN-6 is, but usually only with government permission. The FN-6 is an export version of the QW-1. There is an improved version of the QW-1 (QW-2) that is also not for export.
Thousands of Chinese portable anti-aircraft missiles have been exported in the last decade, many to Moslem (and pro-Syrian rebel) countries like Bangladesh, Malaysia, and Pakistan. The QW-2 is also built under license by Pakistan and Iran and some missiles from these countries have gone to the black market. The FN-6s in Syria appear to have brought down a few helicopters but some have failed to work. This might be the result of age or poor treatment by the original owner. Qatar obtained these missiles earlier this year and passed them on to the rebels.
Meanwhile, there’s lots of evidence that the QW-1 and QW-2 are on the black market. For example, two years ago a naturalized American citizen, Yi Qing Chen was sentenced to 25 years in prison for smuggling drugs, cigarettes, and Chinese QW-2 shoulder fired surface-to-air missiles into the United States. In this case the missiles never made it out of China because Chen was arrested before that part of the deal could be completed. There was convincing evidence that Chen had the right connections in China to get the missiles. Chen was also the first person prosecuted (and given the mandatory 25 year sentence) under a 2004 law dealing with attempting to smuggle such missiles into the United States.
Chen offered to get 200 of the QW-2 missiles, for $91,500 each, and deliver them to anywhere in southern California. Chen also described how he would bribe customs inspectors in the United States and arrange for phony purchase orders from the armed forces of another country, so the missiles could be bought and shipped from China (where he had contacts with the manufacturer who would go along with deals like this). The key element here was knowing who to bribe and the ability to obtain convincing false documents.
While many criminal organizations around the world (like the Taliban, African warlords, and South American drug gangs) have obtained and used missiles like this, it's been very difficult to get these weapons into the United States. This is partly out of self-interest. Commercial aviation is used by just about everyone, and American law enforcement agencies at all levels let it be known that anyone reporting attempts to sell such missiles would be well rewarded. Thus there have been no incidents of such missiles being used in the United States, but there have been many arrests of people attempting to traffic in these weapons (which are compact and weigh less than 20 kg/44 pounds). But the danger is there, as such weapons have been used by gangsters, rebels, and terrorists in South America, Asia, and Africa.
The QW-1/FN-6 is a 17 kg (37 pound) system that includes the launcher/storage tube, missile, and sighting and firing gear. The missile has a max range of five kilometers and max altitude of four kilometers. Minimum altitude is 30 meters. The system is 1.45 meters (4.5 feet) long and the missile is 71mm in diameter. The manufacturer states that the missile has a 70 percent probability of hitting aircraft within range.