Full Disclosure mailing list archives
Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool
From: "lsi" <stuart () cyberdelix net>
Date: Sun, 23 May 2010 19:17:13 +0100
On 23 May 2010 at 16:34, Thor (Hammer of God) wrote: From: "Thor (Hammer of God)" <Thor () hammerofgod com> To: "full-disclosure () lists grok org uk" <full- disclosure () lists grok org uk> Date sent: Sun, 23 May 2010 16:34:24 +0000 Subject: Re: [Full-disclosure] denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool
And where's the part where the system was rendered unbootable?
The unbootable part comes when you replace NDIS.SYS. Unless you know to replace the registry keys first, which is certainly not obvious from the MRT log.
And how did your users get infected with Cutwail? Let me guess... they are all still running XP and you've got them running as local administrators right? And they get to download codecs "willy nilly" and are probably using Bittorrent to get illegal copies of software pre-infected with cutwail, right?
How do I know how they got infected? These are all third-party companies (my customers), sometimes when they have cash problems, they don't call me, they try and do it themselves, or do nothing. I might not see them for months. They don't want to upgrade - they heard about Vista (LOL) and they don't have, or don't want to spend the money. This is reality, not some managed datacentre in Redmond.
local administrators
Their apps needed it last I checked. I didn't set up their machines. They have not asked me to look at that. I have enough trouble getting work OK'd without putting my neck on the line suggesting a configuration change which I cannot guarantee will not cause instability, particularly with their legacy and unsupported software, of which there is plenty. Again, this is reality, not some managed datacentre in Redmond.
Bittorrent
No, like this: "Stuart, need your help. My computer has a virus. Yesterday night I opened an email that I was expecting from a Bernice. It turned out that it was the wrong Bernice and it was a virus. It loaded Security Essentials 2010 which is a scarevirus to make the user believe that there are virus a pay for their software which does nothing anyway. It has loaded a virus in the registry file. There is a lot about it on the net. I then found a PC tools download to remove. However when I turned mycomputer off it does not now allow me to log on. I have turned it off. I am without a PC now. Can you come tomorrow to resolve it for me? Many thanks. Please let me know ad I need it urgently."
Regardless, let's see if we have your advisory correct. In order to be a victim of this "Denial of Service Vulnerability" we must first get infected with something like Cutwail
true
that runs with user interaction
false. Cutwail has no known infection vectors. However, Cutwail is just an example.
interaction and also requires administrator privileges (you can see that NDIS.SYS was altered).
When I am logged in as Admin and try to replace NDIS.SYS, Windows File Protection replaces it. Why did WFP fail to protect the file against Cutwail in the first place, and how can a virus replace NDIS.SYS using Administrative privs, if I cannot do it myself when Administrator?
Of course, your AV must be at least 2 years old too.
false, it was up-to-date, although I am questioning its effectiveness
Then, once we get infected with malware, we run MRT, and see in the logs that it was successfully removed and requires a reboot.
Actually, AV found the virus in NDIS.SYS but could not remove it. So I ran MRT because I thought that a Microsoft product would know this is a Windows file that cannot simply be deleted. MRT says it's done and needs reboot, so I reboot... and the system is toast. To clarify, in this particular case, the first reboot, you can login in normal mode, but cannot use any network adapters (code 39 - driver corrupted or missing). Reinstalling the drivers doesn't help. So then you think, oh that's because NDIS was trashed by MRT, so I'll just replace NDIS.SYS.... And thats when you get the BSOD on boot to normal mode. So then you need to figure out that the cause of that BSOD is a missing registry key, then you need to figure out which keys (there are three, for each controlset), then you need to get the correct keys from a clean machine, then you need to figure out how to replace the keys (some of them cannot be imported with mere Administrative permissions). However, just last week I also fixed a problem with the userinit registry key, also mysteriously deleted - why would a virus trash its host? Answer: it doesn't, I think it was MRT that trashed it. A missing userinit key means instant logoff on logon, even in safe mode as Administrator. I might be able to dig up the MRT log for that machine (would be interesting to see whether it was in fact MRT that did it). Want to place bets now?
From a quick look at the web, MRT has also in the past deleted
Internet Explorer (iexplore.exe). Oh, the poetry.... The point of my mail was that anyone can innocently run MRT and it may trash their box. This is due to one or more design flaws in the MRT, and in Windows itself. Are you saying I should just sit on this info? If someone had told me MRT was going to trash my customer's machine, I would not have wasted most of last week fixing it. Stu
-----Original Message----- From: full-disclosure-bounces () lists grok org uk [mailto:full-disclosure- bounces () lists grok org uk] On Behalf Of lsi Sent: Sunday, May 23, 2010 9:16 AM To: full-disclosure () lists grok org uk Subject: [Full-disclosure] denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool platforms affected: Windows distribution: wide severity: high Description of the vulnerability: The Microsoft Malicious Software Removal Tool (MRT) is a program used to remove malware from infected Windows systems. However, MRT does not always correctly repair the system. In at least one case, the changes made by MRT can render the system unbootable (log below). Repair can be time-consuming and expensive, particularly as the error messages and log files of the software concerned are cryptic and uninformative, or non-existent. As MRT runs automatically in the background once a month, these changes to the system may be made without the knowledge of an Administrator (or even the user). Suspected cause: Missing logic in MRT to repair the system, rather than just deleting stuff willy- nilly. Recommendations: 1. Do not run MRT manually. 2. Disable MRT if possible, especially on mission-critical machines. 3. Do not use Windows. Details of notification to vendor: None. Sample of the fault: Microsoft Windows Malicious Software Removal Tool v3.7, May 2010 Started On Tue May 18 21:24:47 2010 Quick Scan Results for XXXXXXXXXXXXXXXXXXXXX: ---------------- Threat detected: VirTool:WinNT/Cutwail.L driver://NDIS file://C:\WINDOWS\system32\drivers\NDIS.sys SigSeq: 0x00008A78910FD971 SHA1: DEFB65309ABB3DD81F223ABA7CDB9EB26D66611A regkey://HKLM\SYSTEM\CURRENTCONTROLSET\CONTROL\SAFEBOOT\NETW ORK\NDIS safeboot://HKLM\SYSTEM\CURRENTCONTROLSET\CONTROL\SAFEBOOT\NET WORK\NDIS service://NDIS Quick Scan Removal Results ---------------- Start 'remove' for regkey://HKLM\SYSTEM\CURRENTCONTROLSET\CONTROL\SAFEBOOT\NETW ORK\NDIS Operation succeeded ! Start 'remove' for service://NDIS Operation was scheduled to be completed after next reboot. Start 'remove' for safeboot://HKLM\SYSTEM\CURRENTCONTROLSET\CONTROL\SAFEBOOT\NET WORK\NDIS Operation succeeded ! Start 'remove' for driver://NDIS Operation was scheduled to be completed after next reboot. Start 'remove' for file://\\?\C:\WINDOWS\system32\drivers\NDIS.sys Operation succeeded ! Results Summary: ---------------- For cleaning VirTool:WinNT/Cutwail.L, the system needs to be restarted. Microsoft Windows Malicious Software Removal Tool Finished On Tue May 18 21:31:29 2010 Return code: 10 (0xa)
--- Stuart Udall stuart at () cyberdelix dot net - http://www.cyberdelix.net/ --- * Origin: lsi: revolution through evolution (192:168/0.2) _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool lsi (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool Thor (Hammer of God) (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool lsi (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool webDEViL (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool Thor (Hammer Of God) (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool lsi (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool Christian Sciberras (May 23)
- Re: denial-of-service vulnerability in theMicrosoft Malicious Software Removal Tool Larry Seltzer (May 23)
- Re: denial-of-service vulnerability in theMicrosoft Malicious Software Removal Tool Thor (Hammer of God) (May 23)
- Re: denial-of-service vulnerability in theMicrosoft Malicious Software Removal Tool Christian Sciberras (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool lsi (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool Thor (Hammer of God) (May 23)
- Re: denial-of-service vulnerability in the Microsoft Malicious Software Removal Tool lsi (May 23)