Threat Encyclopedia

TROJ_DROPPR.AS

Malware type: Trojan

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

Low

Distribution potential:

Low

Description: 

A Trojan horse program is a malware that is not capable of automatically spreading to other systems. Trojans are usually downloaded from the Internet and installed by unsuspecting users.

Trojans typically carry payloads or other malicious actions that can range from the mildly annoying to the irreparably destructive. They may also modify system settings to automatically start. Restoring affected systems may require procedures other than scanning with an antivirus program.

For additional information about this threat, see:

Description created: Jun. 24, 2010 7:26:18 AM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 40,960 Bytes

Initial samples received on: Jun 21, 2010

Details:

Installation

This Trojan drops the following file(s):

  • %System%\uypw.uzc
  • %User Temp%\3A.tmp

(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.%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. )

Other System Modifications

This Trojan modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe rundll32 uypw.uzc uhwast3"

(Note: The default value data for the said registry entry is Explorer.exe.)

Download Routine

This Trojan connects to the following Web site(s):

  • http://{BLOCKED}ost.net/images/top3c.gif

It accesses Web sites to download the following file(s):

  • %User Temp%\bieqyl.exe

Affected Platforms

This Trojan runs on Windows 98, ME, NT, 2000, XP, Server 2003.


Revision History:

First pattern file version: 7.342.08
First pattern file release date: Jul 28, 2010

SOLUTION


Minimum scan engine version needed: 8.900

Pattern file needed: 7.513.00

Pattern release date: Oct 4, 2010


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

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

 Step 1: Identify and terminate files detected as TROJ_DROPPR.AS  [learn how]

*Note:

  1. For Windows 98 and ME users, Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. 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.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

 Step 2:  Restore this modified registry value  [learn how]

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 NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe rundll32 uypw.uzc uhwast3"
      To: Shell = "Explorer.exe"

 Step 3:  Search and delete these files  [learn how]

*Note: There may be some component files that are hidden. Please make sure you uncheck Hide protected operating system files in Folders Option>View tab, and then check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.

  • %System%\uypw.uzc
  • %User Temp%\3A.tmp
  • %User Temp%\bieqyl.exe

 Step 4: Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPR.AS  

*Note: 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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