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TROJ_COMREROP.B

January 02, 2013
 ALIASES:

Trojan:Win32/Comrerop (Microsoft); Downloader.a!zc (McAfee); Suspicious.Graybird.1 (Symantec); Trojan-Downloader.Win32.Agent.txeb (Kaspersky); Packer.NSAnti.Gen (v) (Sunbelt); Gen:Trojan.Heur.PT.emGdaCnrXCg (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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:

66,265 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Jan 2013

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.

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "%System Root%\{malware file name}.exe"

It registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CLASSES_ROOT\laji

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0\
FLAGS

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0\
0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0\
0\win32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0\
HELPDIR

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}\ProxyStubClsid

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}\ProxyStubClsid32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}\TypeLib

HKEY_CLASSES_ROOT\CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}\InprocServer32

HKEY_CLASSES_ROOT\IE¸¨Öú¹¤¾ß.Class

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
dllname = "8989"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects
NoExplorer = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
NoExplorer = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
pcmac = "00-50-56-8E-00-02"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
posturl = "tj.yuerrq.com"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
id = "admin"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
ver = "1.0.0.1"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
c = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
c1 = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
laji
geturl = "http://asd.{BLOCKED}w.com:3389/q.txt"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}\TypeLib
Version = "4.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
ProgID = "IE¸¨Öú¹¤¾ß.Class"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}\InprocServer32
ThreadingModel = "Apartment"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
TypeLib = "{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
VERSION = "4.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
IE¸¨Öú¹¤¾ß.Class
Clsid = "{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
ProxyStubClsid = "{00020424-0000-0000-C000-000000000046}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
ProxyStubClsid32 = "{00020424-0000-0000-C000-000000000046}"

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://asd.{BLOCKED}w.com:3389/c.txt
  • http://tj.{BLOCKED}q.com/123/count.asp

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

Close all opened browser windows

Step 4

Delete this registry key

[ 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_CLASSES_ROOT
    • laji
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
    • Browser Helper Objects
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib
    • {2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}
    • 4.0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0
    • FLAGS
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0
    • 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0\0
    • win32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}\4.0
    • HELPDIR
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
    • {1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
    • ProxyStubClsid
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
    • ProxyStubClsid32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
    • TypeLib
  • In HKEY_CLASSES_ROOT\CLSID
    • {16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
    • InprocServer32
  • In HKEY_CLASSES_ROOT
    • IE¸¨Öú¹¤¾ß.Class

Step 5

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {malware file name} = "%System Root%\{malware file name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • dllname = "8989"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • NoExplorer = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
    • NoExplorer = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • pcmac = "00-50-56-8E-00-02"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • posturl = "tj.yuerrq.com"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • id = "admin"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • ver = "1.0.0.1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • c = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • c1 = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\laji
    • geturl = "http://asd.{BLOCKED}w.com:3389/q.txt"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}\TypeLib
    • Version = "4.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
    • ProgID = "IE¸¨Öú¹¤¾ß.Class"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}\InprocServer32
    • ThreadingModel = "Apartment"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
    • TypeLib = "{2EF23F42-6E17-429A-BF3F-D5EECFFE8E5B}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}
    • VERSION = "4.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\IE¸¨Öú¹¤¾ß.Class
    • Clsid = "{16B98E57-6EEB-4B62-BE45-1CB754E77B7D}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
    • ProxyStubClsid = "{00020424-0000-0000-C000-000000000046}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{1616CFBE-1232-426D-ADD7-BAF3D4ACC51F}
    • ProxyStubClsid32 = "{00020424-0000-0000-C000-000000000046}"

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_COMREROP.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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