Phishers send you a message with a link to a website that looks just like MyEtherWallet, EtherDelta, Paypal, or your bank, but is not the real website. They steal your information and then steal your money.
Use the EAL or MetaMask Chrome Extension to block malicious websites.
Always check the URL:
https://www.myetherwallet.com.
Always make sure the URL bar has MYETHERWALLET LLC [US] in green.
Do not trust messages or links sent to you randomly via email, Slack, Reddit, Twitter, etc. Always navigate directly to a site before you enter information. Do not enter information after clicking a link from a message or email.
Install an AdBlocker and do not click ads on your search engine (e.g. Google).
That's what I was almost phished by. Checking URL whether real one or not is very important. I always check after coming across the incident.