It sure caught me by surprise. After Microsofts early warning indicated that the five vulnerability disclosures this week would be no more than “Important”—as opposed to “Critical”—I figured no biggie, I went out for the day.
Microsoft explains their reasoning for the “Important” classification for this bug: “… because it was not an Internet-facing technology and because the service is not installed by default on Windows systems.”
This is dissatisfying and possibly disingenuous. Microsoft makes no bones about recommending that all organizations that use Exchange use WINS (along with DNS) for their name resolution. Many important functions of Exchange Server still rely on it. And its not the only application that requires WINS.
Its true, as Microsoft says, that WINS isnt, or at least neednt be, an Internet-facing technology. If your firewalls havent been blocking port 42 by now, they should be. But thats only part of the problem. Many worms, once they penetrate a system, use other techniques to spread. For example, if someone were to infect their PC with the Maslan worm, it would use that computer to attack others on the local network with the LSASS and RPC/DCOM vulnerabilities.
Its not hard to imagine a future version of Maslan adding the WINS exploit to its quiver. At that point all the unpatched Exchange servers on the internal network are exploitable. So much for the exploit not being “wormable.”
I should say that its good to see Microsoft patch an important NT4 bug, and the WINS bug isnt the only one. When the WINS bug went public (thanks to the Secunia and their usual reckless judgment) I figured that Microsoft wouldnt be able to fix it before the end of the year. After that point they changed their policies for Windows NT 4 support, but exactly what they extended beyond the end of the year is still ambiguous from their statements. Microsoft said that they also had received responsible, confidential disclosure of the bug from “Kostya Kortchinsky from CERT RENATER” and credited him in the bulletin. I knew Microsoft wouldnt be able to put a finished patch together in the amount of time Secunia gave them.
Another patch, MS04-042, was NT4-only. It allowed a DHCP client to take control of an NT4 DHCP server. Ill just say ditto to my previous lecture on exploits from the internal network.
There were also code execution bugs in applications Hyperterminal and Wordpad. I have to agree that these would be tough to exploit and certainly arent wormable.
I have to think that Microsoft knows better than the excuses they put up as mitigating circumstances, especially for the WINS bug. We can only hope that no clever exploit comes out, at least anytime soon. It is possible to protect yourself, even without the patch, but the first thing you need to do is to understand how serious the problem is, and Microsofts explanations are no help in that regard.
Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983.
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