If not already done so, your number one priority should be to evaluate, test then deploy the critical security patch for supported Windows operating systems that was part of Microsoft’s out-of-band MS08-067 release last week.
In a nutshell, this vulnerability has already seen real exploits on the rise in the wild where unpatched systems could easily fall prey to remote malicious RPC attacks against the Windows Server/Browser service via TCP/135 and TCP/445 - all without any form of authentication or authorization. An infected machine can potentially become a unwilling host for self-replicating, wormable exploits against other unsuspecting machines in the network, thereby jeopardizing the security of any connected nodes.
To safeguard against similar incidents in the future, consider disabling unwanted services on Windows client machines (laptops and desktops) to harden them from becoming victims. I published an article that discussed this topic some years back; look for “Windows NetBIOS Protection: Closing The Door Ajar @ Home” here. For Windows servers, keep a close tab on security patch management that should be part of your standard IT operational process and procedure.
Technorati tags: Security