|SANS Top-20 Entry:
W5 Windows Remote Access Services
NETBIOS -- Unprotected Windows Networking Shares
Microsoft Windows provides a host machine with the ability to share files or folders across a network with other hosts through Windows network shares. The underlying mechanism of this feature is the Server Message Block (SMB) protocol, or the Common Internet File System (CIFS). These protocols permit a host to manipulate remote files just as if they were local.
Although this is a powerful and useful feature of Windows, improper configuration of network shares may expose critical system files or may provide a mechanism for a nefarious user or program to take full control of the host. One of the ways in which I-Worm.Klez.a-h (Klez Family) worm, Sircam virus (see CERT Advisory 2001-22) and Nimda worm (see CERT Advisory 2001-26) spread so rapidly in 2001 was by discovering unprotected network shares and placing copies of themselves in them. Many computer owners unknowingly open their systems to hackers when they try to improve convenience for co-workers and outside researchers by making their drives readable and writeable by network users. But when care is taken to ensure proper configuration of network shares, the risks of compromise can be adequately mitigated.