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TROJ_AGENT.CHO

October 09, 2012
 Analysis by: Nice Yutuc
 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:

53,816 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 Dec 2011

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.

Installation

This Trojan drops the following copies of itself into the affected system and executes them:

  • %System%\{8 random characters}.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
vcspnet = "%System%\{8 random characters}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
vcspnet = "%System%\{8 random characters}.exe"

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\{8 random characters}.exe = "%System%\{8 random characters}.exe:*:Enabled:Internet Explorer"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Windows%\explorer.exe = "%Windows%\explorer.exe:*:Enabled:Internet Explorer"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
5203:TCP = "5203:TCP:*:Enabled:WWW"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
53:UDP = "53:UDP:*:Enabled:DNS"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
80:TCP = "80:TCP:*:Enabled:WWW"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
25:UDP = "25:UDP:*:Enabled:SMTP"

HOSTS File Modification

This Trojan adds the following strings to the Windows HOSTS file:

  • 192.168.0.101 www.trendmicro.com
  • 192.168.0.101 trendmicro.com
  • 192.168.0.101 rads.mcafee.com
  • 192.168.0.101 customer.symantec.com
  • 192.168.0.101 liveupdate.symantec.com
  • 192.168.0.101 us.mcafee.com
  • 192.168.0.101 updates.symantec.com
  • 192.168.0.101 update.symantec.com
  • 192.168.0.101 www.nai.com
  • 192.168.0.101 nai.com
  • 192.168.0.101 secure.nai.com
  • 192.168.0.101 dispatch.mcafee.com
  • 192.168.0.101 download.mcafee.com
  • 192.168.0.101 www.my-etrust.com
  • 192.168.0.101 my-etrust.com
  • 192.168.0.101 mast.mcafee.com
  • 192.168.0.101 ca.com
  • 192.168.0.101 www.ca.com
  • 192.168.0.101 networkassociates.com
  • 192.168.0.101 www.networkassociates.com
  • 192.168.0.101 avp.com
  • 192.168.0.101 www.kaspersky.com
  • 192.168.0.101 www.avp.com
  • 192.168.0.101 kaspersky.com
  • 192.168.0.101 www.f-secure.com
  • 192.168.0.101 f-secure.com
  • 192.168.0.101 viruslist.com
  • 192.168.0.101 www.viruslist.com
  • 192.168.0.101 liveupdate.symantecliveupdate.com
  • 192.168.0.101 mcafee.com
  • 192.168.0.101 www.mcafee.com
  • 192.168.0.101 sophos.com
  • 192.168.0.101 www.sophos.com
  • 192.168.0.101 symantec.com

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.652.06

FIRST VSAPI PATTERN DATE:

18 Dec 2011

VSAPI OPR PATTERN File:

8.653.00

VSAPI OPR PATTERN Date:

19 Dec 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

Identify and terminate files detected as TROJ_AGENT.CHO

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • vcspnet = "%System%\{8 random characters}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • vcspnet = "%System%\{8 random characters}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\{8 random characters}.exe = "%System%\{8 random characters}.exe:*:Enabled:Internet Explorer"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Windows%\explorer.exe = "%Windows%\explorer.exe:*:Enabled:Internet Explorer"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • 5203:TCP = "5203:TCP:*:Enabled:WWW"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • 53:UDP = "53:UDP:*:Enabled:DNS"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • 53:UDP = "53:UDP:*:Enabled:DNS"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • 25:UDP = "25:UDP:*:Enabled:SMTP"

Step 4

Remove these strings added by the malware/grayware/spyware in the HOSTS file

[ Learn More ]
    192.168.0.101 www.trendmicro.com
    192.168.0.101 trendmicro.com
    192.168.0.101 rads.mcafee.com
    192.168.0.101 customer.symantec.com
    192.168.0.101 liveupdate.symantec.com
    192.168.0.101 us.mcafee.com
    192.168.0.101 updates.symantec.com
    192.168.0.101 update.symantec.com
    192.168.0.101 www.nai.com
    192.168.0.101 nai.com
    192.168.0.101 secure.nai.com
    192.168.0.101 dispatch.mcafee.com
    192.168.0.101 download.mcafee.com
    192.168.0.101 www.my-etrust.com
    192.168.0.101 my-etrust.com
    192.168.0.101 mast.mcafee.com
    192.168.0.101 ca.com
    192.168.0.101 www.ca.com
    192.168.0.101 networkassociates.com
    192.168.0.101 www.networkassociates.com
    192.168.0.101 avp.com
    192.168.0.101 www.kaspersky.com
    192.168.0.101 www.avp.com
    192.168.0.101 kaspersky.com
    192.168.0.101 www.f-secure.com
    192.168.0.101 f-secure.com
    192.168.0.101 viruslist.com
    192.168.0.101 www.viruslist.com
    192.168.0.101 liveupdate.symantecliveupdate.com
    192.168.0.101 mcafee.com
    192.168.0.101 www.mcafee.com
    192.168.0.101 sophos.com
    192.168.0.101 www.sophos.com
    192.168.0.101 symantec.com

"

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_AGENT.CHO. 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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