Microsoft believes hackers have been targeting Skype accounts since early August. When Microsoft integrated Skype logins with general Microsoft account logins, your old Skype username and password might be an unintentional and weak back door straight into your main Microsoft account.
The Verge has a detailed article on the attacks, and also simple-to-follow instructions to ensure your account is secure, which we have replicated below. Click HERE to read the complete article.
1. Go to https://account.microsoft.com, if you're already signed in, sign out.
2. Enter your Skype name, not your Microsoft Account email address, and use your Skype password to sign-in
3. If you've linked your Microsoft Account previously, you'll be prompted to sign-in and merge the accounts to create a Skype alias
Once the two accounts are properly merged, Microsoft creates a Skype alias to let you keep signing in with a Skype username. You can continue using this or disable it under the aliases preferences, to ensure nobody can try to sign in with your Skype username. Either way, you won't be able to use your old Skype password anymore, and attackers will have to know the email address associated with your account.
Your alias preferences can be found HERE.