Analysis by: Karl Dominguez
 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 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: Varies
File Type: PE
Memory Resident: No
Initial Samples Received Date: 27 May 2010
Payload: Drops files

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.

Other Details

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

  • %System%\{random file name}.dll - detected as BKDR_REMOSH.SMF

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It does the following:

  • Queries the following registry entry to enumerate network related services:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
    Windows NT\CurrentVersion\Svchost\netsvcs


    Default Services in NETSVCS which this backdoor may use are as follows:
    • 6to4
    • AeLookupSvc
    • AppInfo
    • AppMgmt
    • AudioSrv
    • BDESVC
    • BITS
    • Browser
    • CertPropSvc
    • CryptSvc
    • DHCP
    • DMServer
    • ERSvc
    • EapHost
    • EventSystem
    • FastUserSwitchingCompatibility
    • HidServ
    • IKEEXT
    • Ias
    • Iprip
    • Irmon
    • LanmanServer
    • LanmanWorkstation
    • LogonHours
    • MMCSS
    • Messenger
    • NWCWorkstation
    • Netman
    • Nla
    • Ntmssvc
    • Nwsapagent
    • PCAudit
    • ProfSvc
    • Rasauto
    • Rasman
    • Remoteaccess
    • SCPolicySvc
    • SENS
    • SRService
    • Schedule
    • Seclogon
    • SessionEnv
    • Sharedaccess
    • ShellHWDetection
    • Tapisrv
    • TermService
    • Themes
    • TrkWks
    • W32Time
    • WZCSVC
    • WmdmPmSN
    • WmdmPmSp
    • Wmi
    • browser
    • gpsvc
    • helpsvc
    • hkmsvc
    • iphlpsvc
    • lanmanserver
    • msiscsi
    • napagent
    • schedule
    • seclogon
    • uploadmgr
    • wercplsupport
    • winmgmt
    • wscsvc
    • wuauserv
    • xmlprov
  • Checks service names found if it already exists in the following registry key:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services


    If the service does not exists, this backdoor uses Network Management as its service name for its dropped .DLL file component. The dropped .DLL then deletes this backdoor once it has been executed.

    However, if all service names in NETSVCS already exists, it then uses the following service name:
    • Network Management

    The dropped .DLL deletes this backdoor once it has been executed.

NOTES:
This is Trend Micro's detection for malware generated by the hacking tool HKTL_REMOSH.

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI OPR PATTERN File: 7.779.00
VSAPI OPR PATTERN Date: 20 Jan 2011

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

Remove the malware/grayware file dropped/downloaded by BKDR_REMOSH.SML

Step 3

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


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