...though not many people here are affected.
Posted on 04/16/2007 8:54:40 AM PDT by ShadowAce
Attackers are targeting a flaw in the DNS service for Windows server OSes that could hijack the computers that run them, Microsoft warns. The software behemoth advises admins to employ workarounds pending completion of its investigation.
The vulnerability affects Windows 2000 Server, Service Pack 4 and SP 1 and SP2 versions of Windows Server 2003, according to this Microsoft advisory. DNS functionality exposed over port 53 is not at risk. Nor are Windows 2000 Professional, Windows XP and Windows Vista.
An attack can be carried out by executing a stack-based buffer overrun in the DNS Server's remote procedure call (RPC) interface. A successful exploit, in which a specially crafted RPC packet is sent to a targeted machine, could allow an attacker to run code in the security context of the DNS, which by default runs full privileges.
Without elaborating, Microsoft said it is aware of "limited attacks" using the DNS flaw. Fortunately, the SANS Internet Storm Center was a bit more forthcoming, saying it has learned of two US universities that have been attacked, in each case in early April from a source located at 61.63.227.125.
According to SANS, the attack commences with a TCP scan of ports 1024-2048, followed by a TCP connection to the port running the vulnerable RPC service. A Shellcode binds to TCP port 1100 and a VBscript is uploaded, which downloads an executable DUP.EXE. Voila: the machine is pwnd.
It's been a busy few weeks for Microsoft's security peeps. Last week, the company rushed out an emergency update to patch a critical hole in the way Windows handles customized cursors. On Tuesday, the company released a host of fixes as part of its monthly patch cycle. But even before savvy users had a chance to install them, miscreants were already tinkering with several new exploits targeting Microsoft products.
Microsoft has yet to announce plans for a patch. In the meantime, it is providing instructions for workarounds, which include disabling remote access of DNS using RPC. Those who want to automate the disabling of RPC from a large number of domain controllers can find help here. ®
...though not many people here are affected.
Running DNS on a Windows machine that is exposed to the Internet is not a good idea. Use it on your internal network to support AD, but keep it away from the public!
Fixed it for you.
Yes it is .... but some engineers are stupid.
Our IT dept. ordered all copies of Firefox removed because it wasn’t as secure as Internet Explorer — so yes, some engineers are stupid.
#!/bin/sh
Service = {exchange iis dns mssql smtp}
Disclaimer = “,if you have to,”
For i in $Service; do
echo “Running $i on a Windows machine that is exposed to the Internet is not a good idea. Use it $Disclaimer on your internal network to support your company, but keep it away from the public!
done
You might be surprised.
F'rinstance, my in-house public nameservers are NetBSD, but I'm installing an Active Directory box that will require its own local DNS, and I'm not sure I can avoid it being accessible from the outside, given some of what my users need it to do. Windows servers are a pain in the butt.
Anyway, I'm pleasantly surprised by how many professional IT folks are on FR.
I was going from the perspective that this seems to attack servers only, and "not many" is a relative term to the number of desktops/workstations as opposed to those responsible for servers.
I'm not trying to diminish the importance of this, though.
Yup. SRV records probably won't play well with RFC compliant nameservers.
Sometimes the way microsoft breaks everything that it is supposed to interoperate with just astounds me.
Used to be, you could safely deny external TCP traffic to a DNS server, because DNS was alway UDP, except for such things as zone transfers. This reduces the exposure of a DNS server significantly. Unfortunately, you can't do that any more because MS, in their infinite wisdom, decided that DNS should be TCP/UDP. The reason for this has to do with packet-size issues from what I understand. Seems that everyone else on the planet can deal with the packet size limitations of UDP but Microsoft just can't handle it.
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