arrow_back
search
close

BKDR_ZEGOST.SML

January 27, 2014
 Analysis by: Jaime Benigno Reyes
 ALIASES:

Backdoor:Win32/Zegost.AD (Microsoft), Trojan.Win32.Staser.pxf (Kaspersky)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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.

  TECHNICAL DETAILS

File Size:

120,169 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Dec 2013

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 copies of itself into the affected system:

  • %Windows%\{8 random alphanumeric characters}.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Qrstuv Xyabcdef Hij

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_QRSTUV_XYABCDEF_HIJ

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Qrstuv Xyabcdef Hij

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_QRSTUV_XYABCDEF_HIJ

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.192.43:7788
  • mcruandan.{BLOCKED}p.cc:7788

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.454.07

FIRST VSAPI PATTERN DATE:

05 Dec 2013

VSAPI OPR PATTERN File:

10.455.00

VSAPI OPR PATTERN Date:

06 Dec 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Scan your computer with your Trend Micro product and note files detected as BKDR_ZEGOST.SML

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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.

 
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Qrstuv Xyabcdef Hij
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_QRSTUV_XYABCDEF_HIJ
  • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Qrstuv Xyabcdef Hij
  • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_QRSTUV_XYABCDEF_HIJ

Step 5

Search and delete files detected as BKDR_ZEGOST.SML

[ 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.

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZEGOST.SML. 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.


Did this description help? Tell us how we did.