TROJ_JOBPAS.B

October 09, 2012
 Analysis by: Christopher Daniel So
 ALIASES:

Trojan:Win32/AgentBypass (Microsoft), Trojan.Dropper (Symantec), Trojan-Downloader.Win32.Small.cexg (Kaspersky)

 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 Trojan may be dropped by other malware.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

25,600 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

12 Jan 2012

Payload:

Drops files

Arrival Details

This Trojan may be dropped by the following malware:

  • TROJ_ARTIEF.SM3

Other Details

This Trojan deletes itself after execution.

NOTES:

It attempts to drop the following files:

  • %Windows%\msacm32.dll - detected by Trend Micro as BKDR_JOBPAS.A

If dropping %Windows%\msacm32.dll is unsuccessful, it drops the following files:

  • %Windows%\Tasks\msacm32.dll - detected by Trend Micro as BKDR_JOBPAS.A
  • %Windows%\Tasks\task.dll - detected by Trend Micro as TROJ_JOBPAS.C

It then creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
wintask = "rundll32.exe %Windows%\tasks\task.dll,run"

It injects the dropped file %Windows%\msacm32.dll or %Windows%\Tasks\task.dll to explorer.exe.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.716.04

FIRST VSAPI PATTERN DATE:

18 Jan 2012

VSAPI OPR PATTERN File:

8.717.00

VSAPI OPR PATTERN Date:

19 Jan 2012

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/grayware files dropped/downloaded by TROJ_JOBPAS.B

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • wintask = "rundll32.exe %Windows%\tasks\task.dll,run"

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_JOBPAS.B. 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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