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BKDR_DELF.MJZ

October 09, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


This backdoor makes the affected machine use fake DNS servers. This causes users to be redirected to malicious sites without their consent. It uses certain DNS server addresses. Once the affected users access certain websites, they will be redirected to certain IP addresses.

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes then deletes itself afterward.

It opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

322,053 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

21 Oct 2011

Payload:

Connects to URLs/IPs

Arrival Details

This backdoor 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 backdoor drops the following component file(s):

  • %User Temp%\5640.sys - detected as TROJ_DELF.MJZ
  • %System%\c_7265170.nls - non-malicious

(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.. %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.)

It executes then deletes itself afterward.

Other System Modifications

This backdoor adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_5640

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}9.{BLOCKED}2.147.141/chrome/report.html
  • http://{BLOCKED}.{BLOCKED}2.243.64/chrome/report.html
  • http://{BLOCKED}.{BLOCKED}.83.115

However, as of this writing, the said sites are inaccessible.

Download Routine

This backdoor downloads an updated copy of itself from the following website(s):

  • http://{BLOCKED}e1.randomstring.com/update_c1eec.exe

HOSTS File Modification

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

  • ::1 localhost

NOTES:

It makes the affected machine use fake DNS servers. This causes users to be redirected to malicious sites without their consent. It uses the following DNS server addresses:

  • {BLOCKED}6.{BLOCKED}7.152.72
  • {BLOCKED}5.{BLOCKED}2.22.72
  • {BLOCKED}5.{BLOCKED}4.236.192
  • {BLOCKED}6.{BLOCKED}7.152.71
  • {BLOCKED}5.{BLOCKED}2.22.71
  • {BLOCKED}5.{BLOCKED}4.236.191
Once the affected users access any of the following websites, they will be redirected to the corresponding IP addresses mentioned below:
  • www.google.com: {BLOCKED}.{BLOCKED}5.87.99
  • google.com: 87.{BLOCKED}5.87.103
  • google.com.au: 87.{BLOCKED}5.87.104
  • www.google.com.au: 87.{BLOCKED}5.87.147
  • google.be: 77.{BLOCKED}5.87.148
  • www.google.be: 77.{BLOCKED}5.87.149
  • google.com.br: 77.{BLOCKED}5.87.109
  • www.google.com.br: 77.{BLOCKED}5.87.150
  • google.ca: 77.{BLOCKED}5.87.152
  • www.google.ca: 77.{BLOCKED}5.87.153
  • google.ch: 77.{BLOCKED}5.87.155
  • www.google.ch: 77.{BLOCKED}5.87.158
  • google.de: 77.{BLOCKED}5.87.160
  • www.google.de: 77.{BLOCKED}5.87.161
  • google.dk: 92.{BLOCKED}5.87.123
  • www.google.dk: 92.{BLOCKED}5.87.160
  • google.fr: 92.{BLOCKED}5.87.154
  • www.google.fr: 92.{BLOCKED}5.87.134
  • google.ie: 92.{BLOCKED}5.87.170
  • www.google.ie: 92.{BLOCKED}5.87.177
  • google.it: 92.{BLOCKED}5.87.173
  • www.google.it: 92.{BLOCKED}5.87.147
  • google.co.jp: 92.{BLOCKED}5.87.103
  • www.google.co.jp: 84.{BLOCKED}5.87.147
  • google.nl: 84.{BLOCKED}5.87.103
  • www.google.nl: 84.{BLOCKED}5.87.147
  • google.no: 84.{BLOCKED}5.87.103
  • www.google.no: 84.{BLOCKED}5.87.147
  • google.co.nz: 84.{BLOCKED}5.87.103
  • www.google.co.nz: 84.{BLOCKED}5.87.147
  • google.pl: 84.{BLOCKED}5.87.103
  • www.google.pl: 64.{BLOCKED}5.87.147
  • google.se: 64.{BLOCKED}5.87.103
  • www.google.se: 64.{BLOCKED}5.87.147
  • google.co.uk: 64.{BLOCKED}5.87.103
  • www.google.co.uk: 64.{BLOCKED}5.87.147
  • google.co.za: 64.{BLOCKED}5.87.103
  • www.google.co.za: 64.{BLOCKED}5.87.147
  • www.google-analytics.com: 64.{BLOCKED}5.87.101
  • www.bing.com: 92.{BLOCKED}3.68.97
  • search.yahoo.com: 72.{BLOCKED}.186.249
  • www.search.yahoo.com: 72.{BLOCKED}.186.249
  • uk.search.yahoo.com: 87.{BLOCKED}8.112.8
  • ca.search.yahoo.com: 100.6.{BLOCKED}9.84
  • de.search.yahoo.com: 87.248.{BLOCKED}2.8
  • fr.search.yahoo.com: 87.248.{BLOCKED}2.8
  • au.search.yahoo.com: 87.248.{BLOCKED}2.8
  • ad-emea.doubleclick.net: 64.{BLOCKED}5.87.101
  • www.statcounter.com: 64.{BLOCKED}5.87.101
  • www.google-analytics.com: 64.{BLOCKED}5.87.101
  • ad-emea.doubleclick.net: 64.{BLOCKED}5.87.101
  • www.statcounter.com: 64.{BLOCKED}5.87.101

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.512.09

FIRST VSAPI PATTERN DATE:

21 Oct 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

Remove malware files dropped/downloaded by BKDR_DELF.MJZ

    TROJ_DELF.MJZ

Step 3

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_5640

Step 4

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

[ Learn More ]
    ::1             localhost
"

Step 5

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you 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.

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_DELF.MJZ. 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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