Only a third of them required any credentials beyond an email address -- additional information like a credit card, phone number, or filling out a captcha.
Captchas are used by freemail services to prevent automatic creation of a huge number of email accounts and to protect automatic form submissions on blogs, forums and article directories.
According to the report, the feature was introduced after the discovery that some bots can successfully go through the company's regular captcha-security feature.
