They are the worst cause most times airdrop do require you filling personal information and many others even go as far as to ask for verifications, which might be use for fraudulent activities without you knowing it and in terms of fake ico, this might be caused due to our negligence, unable to properly read the whitepaper what the project seems to bring and if truly they can keep to their work.
Also try to see if the individuals in charge are popular known or they have handled other projects before then that actually supplied what they had offer before then.
Unable to do such research, usually lead to us been scammed by this ico.
Always do more research about a project before going into it, don't just take the word of others, the best assurance is when you make a proper research yourself
That's been a major issue for me.
For a telegram based airdrop, there's one major telling sign. If you see a bot and there's 'made with @mannybot' then it's probably a scam.
@mannybot is a free telegram bot creating service. Legitimate ICOs would not mind spending money on a telegram based ICO
I also look out for spelling and the team itself. If the spelling on the website is bad or there are very little details about the team, I am usually wary.
Lastly, there are services like airdropkings that try to promote only legitimate airdrop. You can check out for others on twitter
I can't always be sure so it's like in taking a risk. Some have turned out to be real though and I'm grateful for those ones. For the fake airdrops, I simply tell myself to ignore. No use crying over split milk