How to discover non-listed scam sites?

5 Checks you should do:

1. Always check their advertising rates if they payout more than they ask for an ad something is fishy. Such a model is economicaly unsustainable.
2. Do a whois search, in Linux and Mac type "whois domainname".com to find info about who hosts the site. On windows you can go to whois.net and type in the domainname. If the server is located in some exotic place like China it's a sign. If the name of the owner is hidden it could also be a sign but not necessarly.
3. Do a Google search for the name of the site + the word scam. If you get many hits, it should ring a bell, also read the post about it on a few forums.
4. If there are unreasonable rewards per click like $100 or more it's a scam or at least a way to deceive people. Ptc's are always paying bewteen 1/10 of a cent to 2 cent per click. Anything more is doubtful.
5. If it sounds too good to be true it usually is

_Note:

_{Some sites are more clever and build in protection to prevent legal issues. For example some put in their terms payout after 100 years or put 100 USD where USD doesn't stand for USD but for something else or they puta $ sign but it's not US dollars but some high inflated currency or a virtual currency with next to no value.}