Many things have been told already about the latest Skype malware spread via instant messages. However I just wanted to add something not mentioned yet. The first thing is about when the attack was launched first. According to Google Short URL service it first surfaced on Oct 6th :

A new year has broken - a new peer-to-peer botnet is on the rise. It shares some commonalities with the infamous Waledac bot that was taken down in a exemplary effort by Microsoft early last year. Although this new bot has a different code base, it uses the same spreading strategy and also seems to maintain a multi-relay (or peer-to-peer) infrastructure just like its predecessor. Our friends over at ShadowServer have posted an excellent blog entry about this new threat and how it relates to earlier bots.

We are currently analyzing the new family and can confirm peer-to-peer-like behavior. When started, the bot loads a list of 20 hard-coded peers. Each entry contains a unique ID, the peer's IP address and a TCP port it is listening on: