New Stealth Rootkit Steals Windows 7, Server 2008 User Privileges 'On The Fly'

A European researcher has created a rootkit that can evade detection in Windows 7 and Windows Server 2008 machines and reset user passwords.

The rootkit, created by Csaba Barta during the past two-and-half years, was initially a project meant for training purposes. But Barta, a security expert for Deloitte in Hungary who works on penetration testing and forensic cases, says he eventually discovered he could perform new types of attacks with the rootkit, which he plans to deliver to antivirus firms as well as to the International Council of E-Commerce Consultants (EC-Council) for its certified hacker training program.

Barta demonstrated the rootkit for the first time at the recent Hacker Halted conferences in Miami and Cairo. One particularly powerful module of the rootkit is based on the concept of a so-called cached data attack, which had previously been explored by researcher Brendan Dolan-Gavitt, who looked at how Windows handles registry in memory and how a forensic investigator can extract that from the physical memory image, according to Barta.

The cached data attack has to do with how the OS caches data in physical memory. It lets an attacker clear and reset passwords in memory without being detected by the operating system, for example. "After some research on this subject, I ended up in a different solution that allowed the rootkit to temporarily blank the password hash even when the user is logged on. According to my knowledge, the technique mentioned in [Dolan-Gavitt's] article was to modify one specific instance of the hash and after that the user had to do a logout/login in order for the OS to use the new hash," Barta says. "The cached data attack is an attack that is based on the fact that the OS caches data in physical memory in order to use it. If you are able to modify this data you are able to fool the OS to use the modified data."

Barta's rootkit works on most 32-bit versions of Windows, and its ability to steal user privileges on the fly is especially useful, he says. "[You can] start processes on behalf of them without being noticed, even if detailed process tracking is turned on," Barta says.

It also hides files and directories, performs keyboard-logging, and can temporarily "blank" a local user's password even when he is logged in.

"On one side we are very proud of Csaba's results, but on the other hand it is a sad evidence of the fact that there are hidden attacks that surface all the time," says Sean Lim, vice president of the EC-Council. "We plan to incorporate the rootkit in the CEHv7 Training Material to make our students aware of the risks."

Barta says he will try to ensure that AV companies include the rootkit in their scanning databases before he releases the binaries in the CEHv7 training material.

Why the special attention to this particular rootkit? "There are rootkits embedded in malware, but the functionality of them is limited to certain functions," he says.

Even so, rootkits take expertise to pull off. New 64-bit versions of Windows that digitally sign drivers make it more difficult to plant a rootkit in the kernel, Barta notes. "One [needs] really strong basics in using tools, such as a kernel debugger and programming languages like assembly and C, in order to start the implementation [as well]," he says. The attacker first must gain administrative rights to the system, which means unleashing an exploit, password-cracking, or socially engineering it, he says.

Barta says he will continue to add features to his rootkit, including adding network-layer functions, he says. But don't look for him to release the code itself -- he says he won't do that.

"Although developing a rootkit is considered old-school, I think that it is really interesting. By doing it you can really understand how an OS is working. It is also a very precious knowledge in the field of computer forensics," he says.

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