Dima Bekerman, a security researcher at Imperva, explains how easily his Amazon account was broken into. He initially thought it was a run-of-the-mill account breach, but the attack turned into a smokescreen. He noticed that the registration email usernames used a random string of nine or ten letters followed by four numbers. The full blog post, which includes tips on how to prevent these types of attacks, can be found here, however key takeouts are listed below.”]
Source: https://informationsecuritybuzz.com/articles/amazon-account-hacking/