In computer networking, Server Message Block (SMB) operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an authenticated Inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it is often known as “Microsoft Windows Network“.
There is a reason why i posted that definition above ! Windows 7 has a serious technical glitch. Windows 7 has re-introduced the SMB driver, which means that any cracker can gain access to your system remotely and crash it , if it is SMB enabled. Windows Xp, 2k, are NOT affected as they dont have this driver.
This vulnerability has been identified by Laurent Gaffié and he haas blogged it in here .
more technical info here