Threat Encyclopedia


Malware type: Backdoor

In the wild: No

Overall risk rating:


A backdoor program is a Trojan specifically designed to allow malicious users to remotely manipulate affected systems. Like all Trojans, backdoors do not automatically propagate. They are either installed inadvertently by unsuspecting users or intentionally by malicious users.

Backdoors, like other Trojans, typically modify system settings to automatically start. Users may need to terminate backdoors before they can be deleted. Also, restoring affected systems may require procedures other than scanning with an antivirus program.

For additional information about this threat, see:


File type: PE

Memory resident:  Yes

Size of malware: 35,328 Bytes


Arrival Details

This backdoor may be downloaded from remote site(s) by other malware.

It may be dropped by other malware.


This backdoor drops the following file(s):

  • %System%\csrls.dll

(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 Techniques

This backdoor creates the following registry entry(ies) to enable its automatic execution at every system startup:

Athene = "%System%\0b2a0902-ad82-4b0b-bdb9-7158e2c4aee2.exe"

Other System Modifications

This backdoor creates the following registry key(s)/entry(ies):

Athene = "{malware path and filename}"

It modifies the following file(s):

  • %System%\0B2A0902-AD82-4B0B-BDB9-7158E2C4AEE2.EXE

Affected Platforms

This backdoor runs on Windows 2000, XP, Server 2003.


Minimum scan engine version needed: 6.810

Pattern file needed: 7.939.00

Pattern release date: Mar 29, 2011

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.


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 BKDR_AGENT.U  [learn how]


  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:  Delete this 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.

    • Athene = "%System%\0b2a0902-ad82-4b0b-bdb9-7158e2c4aee2.exe"
    • Athene = "{malware path and filename}"

 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%\csrls.dll

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

*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.

 Step 5: Restore this file from backup  

*Note: Only Microsoft-related files will be restored. If this malware/grayware/spyware also deleted files related to programs that are not from Microsoft, please reinstall those programs on your computer again.

  • %System%\0B2A0902-AD82-4B0B-BDB9-7158E2C4AEE2.EXE

Trend Micro offers best-of-breed antivirus and content-security solutions for your corporate network, small and medium business, mobile device or home PC.

Featured Stories

Connect with us on