As certain high school seniors work meticulously this month to finish their early applications to colleges, some may not realize that comments they casually make online could negatively affect their prospects. In fact, new research from Kaplan Test Prep, the service owned by the Washington Post Company, suggests that online scrutiny of college hopefuls is growing.

Of 381 college admissions officers who answered a Kaplan telephone questionnaire this year, 31 percent said they had visited an applicant’s Facebook or other personal social media page to learn more about them — a five-percentage-point increase from last year. More crucially for those trying to get into college, 30 percent of the admissions officers said they had discovered information online that had negatively affected an applicant’s prospects…

There is some reason for concern. Ms. Brown says that most colleges don’t have formal policies about admissions officers supplementing students’ files with their own online research. If colleges find seemingly troubling material online, they may not necessarily notify the applicants involved.

“To me, it’s a huge problem,” said Bradley S. Shear, a lawyer specializing in social media law. For one thing, Mr. Shear told me, colleges might erroneously identify the account of a person with the same name as a prospective student — or even mistake an impostor’s account — as belonging to the applicant, potentially leading to unfair treatment. “Often,” he added, “false and misleading content online is taken as fact.”