Detecting user-mode rootkits

• US 7,874,001 B2
• Filed: 07/15/2005
• Issued: 01/18/2011
• Est. Priority Date: 07/15/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Beck, Douglas Reed, Wang, Yi-Min
• Primary Examiner(s): Moazzami; Nasser
• Assistant Examiner(s): JOHNSON, CARLTON
• Application Number:
  US11/183,225
• Publication Number:
  US 20070022287A1
• Time in Patent Office: 2,013 Days
• Field of Search: None
• US Class Current: 726/23
• CPC Class Codes: G06F 21/554 involving event detection and direct action
• CPC Class Codes: G06F 21/566 Dynamic detection, i.e. detection performed at run-time, e.g. emulation, suspicious activities
• CPC Class Codes: G06F 2221/2105 Dual mode as a secondary aspect
• CPC Class Codes: H04L 63/145 the attack involving the propagation of malware through the network, e.g. viruses, trojans or worms

Abstract

A method and system for determining whether resources of a computer system are being hidden is provided. The security system invokes a high-level function of user mode that is intercepted and filtered by the malware to identify resources. The security system also directly invokes a low-level function of kernel mode that is not intercepted and filtered by the malware to identify resources. After invoking the high-level function and the low-level function, the security system compares the identified resources. If the low-level function identified a resource that was not identified by the high-level function, then the security system may consider the resource to be hidden.

Claims

1. A method in a computer system with a processor and a memory for determining whether a process being hidden is a root process of malware, a root process being a process of the malware whose access to system resources is not filtered by the malware, the method comprising:

invoking by the computer system a high-level function of user mode to identify processes;

invoking by the computer system a low-level function of kernel mode to identify processes;

when a process is identified by the low-level function but not identified by the high-level function, indicating that the process is hidden;

injecting code into code of the hidden process, the injected code for determining whether a resource is hidden from the hidden process; and

after injecting the code,

launching execution of the hidden process; and

during execution of the injected code within the hidden process,

determining whether a resource is hidden from the hidden process; and

upon determining that no resource is hidden from the hidden process, indicating that no resource is hidden; and

when the injected code indicates that no resource is hidden, indicating that the hidden process is a root process.

2. The method of claim 1 including renaming a shell file to a name of an executable file of the root process and launching the renamed shell file as a process so that malware does not infect the process launched from the renamed shell file.

3. The method of claim 2 including executing security code in a process related to the process launched from the renamed shell file.

4. The method of claim 1 including updating a list of directories that may contain malware based on the hidden process.

5. The method of claim 4 wherein a hidden directory is added to the list.

6. The method of claim 4 wherein a directory containing an executable file of a hidden process is added to the list.

7. The method of claim 1 including when it is to be determined whether processes are hidden, downloading from a server code for invoking the high-level function and the low-level function.

8. The method of claim 7 wherein the downloaded code is obfuscated to prevent its detection as performing a security function.

9. A computer-readable storage medium where the medium is not a signal containing instructions for controlling a computer system to perform a security function, by a method comprising:

determining that an executable file executes as a root process of malware, a root process being a hidden process of the malware whose access to system resources is not filtered by the malware by;

injection code into the hidden process the injected code for determining whether a resource is hidden from the hidden process;

launching the execution of the hidden process with the injected code; and

during execution of the injected code within the hidden process,

determining whether a resource is hidden from the hidden process; and

when it is determined that no resource is hidden from the hidden process, indicating that the hidden process is the root process;

renaming a file based on a name of the executable file;

launching the renamed file as a process so that the malware considers the renamed file to be a root process; and

executing security code in a process related to the launched process.

10. The computer-readable storage medium where the medium is not a signal of claim 9 wherein the determining includes identifying a hidden process by invoking a high-level function of user mode and a low-level function of kernel mode to identify processes wherein a hidden process is identified by the low-level function and is not identified by the high-level function.

11. The computer-readable storage medium where the medium is not a signal of claim 9 wherein when it is to be determined whether a process is a root process, downloading from a server code for invoking the high-level function and the low-level function.

12. The computer-readable storage medium where the medium is not a signal of claim 11 wherein the downloaded code is obfuscated to prevent its detection as security code.

13. A computer-readable storage medium where the medium is not a signal containing instructions for controlling a computer system to determine whether a process is hidden, by a method comprising:

invoking a high-level function of user mode to identify processes;

invoking a low-level function of kernel mode to identify processes;

comparing the processes identified by the high-level function and the low-level function;

indicating that a process identified by the low-level function and not identified by the high-level function is hidden;

re-invoking the high-level function and the low-level function to help confirm whether a process that was indicated as being hidden was not started after invoking the high-level function and before invoking the low-level function and was not terminated after invoking the low-level function and before invoking the high-level function; and

when the re-invoking indicates that a process is hidden,

injecting code into the hidden process, the injected code for determining whether a resource is hidden from the hidden process;

launching execution of the hidden process with the injected code; and

when the injected code within the hidden process determines that no resource is hidden from the hidden process, indicating the hidden process is a root process.