Analysis by: Kathleen Notario
ALIASES:

Mal/Generic-L 9W32.SillyDC (Symantec); Worm:Win32/Catchdens.A (Microsoft); Trojan-PSW.Win32.Agent.tur (Kaspersky); Generic.dx!tgk (Mcafee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This worm 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: 183,808 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 25 Aug 2011
Payload: Steals information

Arrival Details

This worm 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 worm drops the following copies of itself into the affected system:

  • %Application Data%\{random folder name}\{random filename}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It creates the following folders:

  • %User Temp%\~INST
  • %Application Data%\{random folder name}

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.. %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • 000C296817CC000329681733

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows\
load
{random filename}.exe = %Application Data%\{random folder name}\{random filename}.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunServices
{random filename}.exe = %Application Data%\{random folder name}\{random filename}.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrrentVersion\Run
{random filename}.exe = %Application Data%\{random folder name}\{random filename}.exe

NOTES:

It does not continue with its routines if the language of the affected system is not Chinese.

It retrieves the following information:

  • Adaper information
  • Computer name
  • Operating system information
It may also steal sensitive information such as usernames and passwords from the following:
  • Active Directory - Bigfoot, VeriSign, and WhoWhere
  • HTTPMail
  • IMAP
  • Internet Account Manager
  • Internet Explorer
  • NNTP
  • Outlook Express
  • POP3
  • SMTP
  • Windows Live

It may send copies of itself as attachment to email messages.

It connects to the following URL:

  • {root domain}{subdomain}{parameter}

where {root domain} may be any of the following:

  • {BLOCKED}w.cn
  • {BLOCKED}rkosoft.net
  • {BLOCKED}s.now.cn
  • www.{BLOCKED}a.com
  • www.{BLOCKED}j.cn
  • www.{BLOCKED}on.net
  • www.{BLOCKED}8.com
  • www.{BLOCKED}ll.net
  • www.{BLOCKED}per.com
  • www.{BLOCKED}ian.com

where {subdomain} may be any of the following:

  • /ip/?q=
  • /ip/ipdomain_contents.php?ip_check=
  • /ips.asp?ip=
  • /bianmingfuwu/ip/?s=
  • /Ip.asp?Action=1&IpStr=
  • tools/nslookup.php4?ns_host=
  • scripts/tools/nslookup.asp?Host=
  • nslookup.php?host={parameter}&submit=Nslookup!
  • cgi-bin/checkhost?keyword=
  • nslookup.php?choice=host&hostip=

where {parameter} may be any of the following:

  • www.{BLOCKED}ha.com
  • www.{BLOCKED}8.net
  • www.{BLOCKED}38.com
  • www.{BLOCKED}3.cn
  • {BLOCKED}er.cn

It performs GET requests to the formed URL. It then parses the contents to search for the following strings:

  • address 
  • address:
  • Address:
  • ip_add.asp?ip=
  • IpStr=
  • ospace;
  • whois.php?ip=

It uses the domains/IP addresses/names that it finds as values for the content of the email that it sends.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.378.08
FIRST VSAPI PATTERN DATE: 25 Aug 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 WORM_AGENT.AUQS

[ 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 NT\CurrentVersion\Windows\load
    • {random filename}.exe = %Application Data%\{random folder name}\{random filename}.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices
    • {random filename}.exe = %Application Data%\{random folder name}\{random filename}.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrrentVersion\Run
    • {random filename}.exe = %Application Data%\{random folder name}\{random filename}.exe

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
%User Temp%\~INST
%Application Data%\{random folder name}

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_AGENT.AUQS. 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.

NOTES:

Recommendation

This malware is detected and removed by the latest Trend Micro anti-malware engine and pattern. Always keep pattern files and engines up-to-date. To know more about updating your Trend Micro product’s pattern, please refer to the following Trend Micro support page:


Note: The steps apply for specific products indicated in the page.

To actively detect and protect your machine, enable real-time scanning of your Trend Micro anti-malware product. Refer to the following Trend Micro support page to know more about enabling real-time scanning in your Trend Micro product:

Enable firewall to protect against threats.
Block malware related websites.
Avoid visiting un-trusted sites that may redirect or download malware into the system.
Update/reset access information such as username/passwords for all sites/applications.
Configure your email server to block or remove email that contains file attachments such as .vbs, .bat, .exe, .pif and .scr files.
Block any file with more than one file type extension.
Avoid opening e-mail attachments unless expected.


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