===> Why this ALERT here? Lots of teachers around the world are using Skype for learning... <===
Summary: An updated do-it-yourself (DIY) Skype spamming tool has been made available for just $10. Skype Flooder by Revi has now hit version 2.0 and can be purchased on underground forums.
To protect yourself from this DIY Skype spamming tool, ensure that only users in your contact list can send you IMs or initiate calls with you. By default, Skype allows anyone to call you.
Here's how to change these settings: Tools => Options… => Privacy => "Allow calls from... people in my Contact list only" and "Automatically receive video and share screens with... people in my Contact list only" and "Allow IMs from... people in my Contact list only."
Via Gust MEES, Kalani Kirk Hausman