Threat Encyclopedia

TROJ_DUQU.DEC

Publish date: October 21, 2011

ANALYSIS BY

Karl Dominguez


PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

OVERALL RISK RATING:
DAMAGE POTENTIAL:
DISTRIBUTION POTENTIAL:
REPORTED INFECTION:

  • Threat Type:Trojan

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW


This malware is possibly connected with DUQU malware, which shares code similarities in STUXNET malware.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

This Trojan is decrypted and loaded by RTKT_DUQU.SME from TROJ_DUQU.ENC. It finds processes related to antivirus programs running in memory. If no match is found, it creates a process of lsass.exe then patches it with the malware code.

However, if any of the said processes is found, it creates a new process of the reference file and patches malware code into it. It may also use processes to inject its code if the process name matches and if the malware is unable to determine the file path. It hooks APIs to load a component in memory, "sortxxx.nls". It connects to an IP address to contact its C&C server. It enables remote attackers to execute arbitrary commands in the affected system including downloading other malicious files. It also reads any certain files to get configuration settings.

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

TECHNICAL DETAILS

File Size:

Varies

File Type:

DLL

Initial Samples Received Date:

19 Oct 2011

Payload:

Compromises system security

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

NOTES:

This Trojan is decrypted and loaded by RTKT_DUQU.SME from TROJ_DUQU.ENC.

It finds the following processes related to antivirus programs running in memory:

  • 360rp.exe
  • 360sd.exe
  • avguard.exe
  • avp.exe
  • bdagent.exe
  • ccSvcHst.exe
  • ekrn.exe
  • fsdfwd.exe
  • Mcshield.exe
  • RavMonD.exe
  • rtvscan.exe
  • tmproxy.exe
  • UmxCfg.exe

If no match is found, it creates a process of lsass.exe then patches it with the malware code.

However, if any of the above-mentioned processes is found, it creates a new process of the reference file and patches malware code into it.

It may also use the following processes to inject its code if the process name matches and if the malware is unable to determine the file path:

  • explorer.exe
  • iexplore.exe
  • svchost.exe
  • winlogon.exe

It hooks the following APIs to load a component in memory, "sortxxx.nls".

  • ZwClose
  • ZwCreateSection
  • ZwMapViewOfSection
  • ZwOpenFile
  • ZwQueryAttributesFile
  • ZwQuerySection

It connects to the following IP address to contact its C&C server:

  • {BLOCKED}3.111.97
  • {BLOCKED}.93.160

It enables remote attackers to execute arbitrary commands in the affected system including downloading other malicious files.

It also reads any of the following files to get configuration settings:

  • %System Root%\inf\cmi4464.pnf - TROJ_DUQU.CFG
  • %System Root%\inf\netp192.pnf - TROJ_DUQU.CFG

SOLUTION

Minimum Scan Engine:

9.200

VSAPI OPR PATTERN File:

8.509.00

VSAPI OPR PATTERN Date:

20 Oct 2011

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by TROJ_DUQU.DEC

Step 3

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DUQU.DEC. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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