Phishing is a scam that involves tricking unsuspecting users into giving up compromising personal information through the use of phony emails that often lead to fake web pages.
In this case, online reports said that these emails tell users that their YouTube account has problems, and that they should click over to the site to resolve them.
Apparently the level of professionalism in the fake emails increased over time.
"While the first e-mail was quite amateuristic in nature and came filled with stuff that should raise quite some warning flags (typos, clumsy phrasing, Youtube instead of YouTube, etc.), the second appeared more genuine and had a body text edited rather professionally," wrote analyst Robin Wauters of TechCrunch.com.
YouTube's partner program allows users to set up a full channel on the site with added benefits provided by YouTube. Users who set up YouTube channels must abide by the site's terms of use, which limit adult content.