They Loved your GPA, Then They saw your Tweets

In the article They Loved your GPA, Then They saw your Tweets it talked about how collage admission offices look at your social media accounts to help determine whether you application gets  accepted. I was surprised when they said "30 percent of the admissions officers said they had discovered information online that ha d negatively affected an applicants prospects". I didn't  realize how many colleges really look through all your social media accounts. I was confused on how the colloges got to see private accounts. Like do they hack your account, and if they do how is it legal? It really makes me really think about what I'm saying, and how it could impact my chance of getting into a college.