US SEC has a complete article on how to avoid getting scammed on the internet, esp. via emails, forums, and investment letters, etc. In short, the protection is to practice “due diligence” and check out reliable sources for verification. What is “due diligence”? It is basically to perform detailed research and investigation, before proceeding with any business investments, acquisition, partnerships, etc. One of the best way is to check the background of the company and do keyword search on the internet. However, we do not recommend calling up the “other party” especially when it involves unsolicited emails from the internet – unless you are a scam baiter or police.
Do check out this website if you would like more information and advise. There is also a page on telltale signs of online investment fraud.