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Remove Mebroot Sinowal Rootkit
Security vendors are reporting a new version of Mebroot, aka Torpig and Sinowal, that has been armored with new functionality to avoid detection. The new variant hooks itself deep within Windows to thwart efforts at spotting it.
Malware writers have added new moves to the notorious Mebroot rootkit.
The malware also goes by the name Sinowal and Torpig, and made headlines late last year when EMC’s RSA security division found a trove of financial data stolen by attackers. Now, security vendors say a new variant has been armed with functionality designed to cloak it as it spreads through drive-by downloads and by exploiting a recent Adobe Reader and Acrobat vulnerability.
“This is the stealthiest rootkit in the wild today,” Jacques Erasmus, director of research at Prevx, told eWEEK. “There are proof-of-concept rootkits that are more stealthy, but in terms of them being able to be implemented for mainstream use, that is still a very long way off.”
Once on your Windows PC, Mebroot delivers a payload that can record keystrokes, sniff HTTP and HTTPS Post requests, and inject arbitrary HTML into Websites, particularly banking sites. But according to security vendors, what’s really new is how Mebroot infects a system. According to researchers at Prevx, Mebroot no longer hooks into the disk.sys driver, but checks to see what lower device \Device\Harddisk0\DR0 is attached to and then hooks the relative driver.
“If the lower driver to which the device is attached is atapi.sys, then atapi.sys will be hooked,” a Prevx researcher explained in a blog post. “If the lower driver is acpi.sys, then that driver will be attacked. ... This is why you can get different results from pc to pc, and from a pc and a virtual machine like VMware.”
In this new version, the malware authors also fixed a bug that had previously made it easier to detect anomalies with the master-boot-record, said Andreas Baumhof, CTO for TrustDefender.
He added that after the initial infection, Mebroot is never present as a file on the hard drive. It gets injected into various kernel drivers during the boot-up procedure and is finally injected into services.exe and svchost.exe. Then it will through IAT compromise all processes to get access to the internal data, he said.
“So altogether, Mebroot is not visible as a kernel driver, not visible as a usermode process, [and] if you scan your hard drive, nothing is found,” he said, adding however that two executables are executed at the time of the initial infection and will be present on the hard drive for a short period in the temp directory.
Prevx has added functionality into its new tool, Prevx 3.0, to help organizations deal with the threat. According to researchers at Symantec and TrustDefender, infections of the new variant do not appear to be extremely widespread at the moment.
"We have seen it 'popping up' on a small amount of servers, and now it almost disappeared again; however, we all know that it won’t take too long before it will reappear again," Baumhof said. "In my opinion, these guys know the workings of the security industry in very much detail, and they don’t want to run the risk of infecting too many computers, for example, to be included in an MSRT, or to face a global targeted alliance against them—as seen, for example, with conficker.c."
Infected System
Mebroot will install Torpig as payload and Torpig is by far the nastiest thing we have ever seen. Generally, it:
* will steal login and other personal or confidential details from banking websites
* can inject any HTML content into any website (websites can be encrypted with or without EV-SSL.) without detection
* can capture CAPCHA and compromize virtual keyboards
* can use the information in real-time to defeat One-Time-Passwords
* has configuration files for many banking sites so that it knows exactly what to look out for
* is incredibly hard to detect
* works system-wide and therefore any browser is affected. (Yes, you heard right. Firefox and Chrome users are also affected)
So how does it work?
Well, we are still reverse-engineering and analyzing the trojan in detail, however after infecting the Master-Boot-Record, it employs a complicated mechanism to injects itself into the ATAPI Harddrive Driver to then inject core windows components (svchost.exe and services.exe) which then will hook/redirect functions for all processes that are used for internet transmissions. What’s important is that your webbrowser (Internet Explorer, Firefox, Opera, Chrome, …) is infected and they don’t even know it!
So what does Mebroot/MBR/Torpig do?
As said before, it is after your login credentials and personal information and the ability to manipulate this data either in real-time or use at a later date. It will either simply steal your data directly as it is typed or inject HTML code into the banking website to gather additional information.
1) Steal authentication data (including defeating virtual keyboards)
The stolen data is stored locally in a file (c:\windows\temp\rg4sfay in our case) and will then transfer this file to the malicious hosts.
2) Inject HTML Code into the banking website to steal additional data. banking services where additional information is requested. However as these forms appear after the customer logged in and come from an apparent trusted site, the success rates for the perpetrators of this trojan are much higher and more effective than ever before.
this Trojan injects itsself into various kernel drivers (atapi.sys in this case) . However this injection is only done in memory and no malicious components are ever written to the harddrive. This is why detection from Antivirus Engines is so low.
However as Torpig wants to steal data from your web browser process, it will hook key functions of the webbrowser process by patching the Import Address Table (IAT).
this Trojan injects itsself into various kernel drivers (atapi.sys in this case) . However this injection is only done in memory and no malicious components are ever written to the harddrive. This is why detection from Antivirus Engines is so low.
However as Torpig wants to steal data from your web browser process, it will hook key functions of the webbrowser process by patching the Import Address Table (IAT).
How can this Trojan be detected?
Well, as you would have guessed, Antivirus detection is almost zero for this new variant. This applies to the dropper/installer as well as to the payload. In fact I haven’t seen a single Antivirus Engine so far that can detect that Torpig is active.
You can detect this trojan as follows (no guarantee as this may change frequently)
* did your computer restart without warning or bluescreen?
* open the command prompt (cmd.exe) and go to the c:\WINDOWS\TEMP directory. Now execute “notepad rg4sfay” and if infected, you’ll see the stolen content. Plese note that this file is hidden and won’t be shown in the windows explorer.
* download Process Explorer from Sysinternals and click on “services.exe” and check for open file handles (in the listbox below) for
1: any file references to \WINDOWS\TEMP\…
2: file reference to \!win$
The trojan can be removed by using the Windows Recovery Console as described.
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