ICOs are inherently risky because they are not regulated, making them vulnerable to fraud. Scammers offering an ICO will attempt to drive the price of the cryptocurrency up to a particular point, at which they will sell their entire interest.
These are some of the signs:
1. Weak Website or White Paper
2. Absence of Named Developers or Team Members
3. No Clear Roadmap
4. Skewed Mining Structure
5. Uncapped Fundraising Goal
6. Evidence of a Pyramid Structure
Source: mobidea.com