Earlier this year, my husband got ripped off by a guy on yahoo auction, and my husband sued him and won the case, getting his money back. I asked my husband to explain the process, and I hope this will help someone if they are unfortunate enough to be in this situation. Sorry, I don't have all the Chinese characters to explain the actual depts, but I will get them and add them when I can.
There is now a special section that handles Internet cases. You go to your local police station and ask to file a complaint relating to Internet fraud. If you have been cheated in some way and want to get your money back, you file as a scam, which is a public issue, not as a consumer issue. (Sorry for the lack of legal lingo) This way seems to be simpler (husband explained why but I need to double-check details) but you can only claim your money back, no other kinds of damages.
The police will ask you where this happened. To make it more convenient for yourself, tell them it happened at the place that will be more convenient to visit the police station. This means, if it is easier for you to report to the police station near your house, you tell them you bought the item online when you were at home. If near work is better, tell them you were in your office at the time. The accused will then have to come to that office nearest the place that is convenient for you. (So, you don't have to worry about going down south if you are in Taipei, for example. In our case, the guy wasn't too happy about making trips from Zhonghua to Taipei, serves him right!)
Keep printed copies of any Q&A or other transactions that you had on yahoo. In my husband's case, he printed out the Q&A where the seller had first said the item had never been used, which was not the truth. You also have your bank book or online printout that shows the ATM transaction.
You will have a chance to tell your side of the story, then the other party will. There will be some kind of mediation. There will be a written agreement and if either party fails to follow it up, the office responsible will take action. (In our case, the seller kept stalling the payment, and after a call from the mediator suggesting he might end up in court after all, money turned up the next day.)
There is no charge for this process, but it can take up some time, as you have to go to the office a couple of times for the meetings.
There are so many bullies in Taiwan who think they can get away with this kind of thing, and the general public feel they have no rights. But, this year I have seen personally and in business, that if you do take a stand when you are in the right, the outcome can be surprisingly satisfying.