ALIASES:

Trojan:Win32/Ertfor.B (Microsoft); ErtFor.d (McAfee); Downloader.MisleadApp (Symantec); Backdoor.Win32.Small.abn (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Generic.Malware.SFDdld.7540660C (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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: 665,676 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 24 Jun 2012

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system:

  • %User Temp%\csrss.exe
  • %User Temp%\svchost.exe
  • %User Temp%\setup.exe
  • %Windows%\setup.exe
  • %User Temp%\win32.exe
  • %Windows%\lsass.exe
  • %User Temp%\spoolsv.exe
  • %User Temp%\avp.exe
  • %Windows%\user.exe
  • %Windows%\debug.exe
  • %User Temp%\msmgm.exe
  • %User Temp%\lsass.exe
  • %Windows%\wininst.exe
  • %Windows%\win32.exe
  • %Windows%\nvsvc32.exe
  • %User Temp%\drweb.exe
  • %User Temp%\win16.exe

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

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRnyc = "%User Temp%\csrss.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRnyc = "%User Temp%\csrss.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRrse = "%User Temp%\svchost.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRrse = "%User Temp%\svchost.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRrvc = "%User Temp%\setup.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRrvc = "%User Temp%\setup.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKevc = "%Windows%\setup.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKevc = "%Windows%\setup.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRsPc = "%User Temp%\win32.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRsPc = "%User Temp%\win32.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKcuc = "%Windows%\lsass.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKcuc = "%Windows%\lsass.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRruf = "%User Temp%\spoolsv.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRruf = "%User Temp%\spoolsv.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRme = "%User Temp%\avp.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRme = "%User Temp%\avp.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKee = "%Windows%\user.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKee = "%Windows%\user.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKaoc = "%Windows%\debug.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKaoc = "%Windows%\debug.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRptc = "%User Temp%\msmgm.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRptc = "%User Temp%\msmgm.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRpuc = "%User Temp%\lsass.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRpuc = "%User Temp%\lsass.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKfre = "%Windows%\wininst.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKfre = "%Windows%\wininst.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKfPc = "%Windows%\win32.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKfPc = "%Windows%\win32.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MKdw+ = "%Windows%\nvsvc32.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MKdw+ = "%Windows%\nvsvc32.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRnsc = "%User Temp%\drweb.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRnsc = "%User Temp%\drweb.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRsPc = "%User Temp%\win16.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HNUGROXRsPc = "%User Temp%\win16.exe"

Other System Modifications

This Trojan deletes the following files:

  • %User Temp%\yawghd72y7huhd.tmp
  • %User Temp%\csrss.exe
  • %User Temp%\svchost.exe
  • %User Temp%\setup.exe
  • %Windows%\setup.exe
  • %User Temp%\win32.exe
  • %Windows%\lsass.exe
  • %User Temp%\spoolsv.exe
  • %User Temp%\avp.exe
  • %Windows%\user.exe
  • %Windows%\debug.exe
  • %User Temp%\msmgm.exe
  • %User Temp%\lsass.exe
  • %Windows%\wininst.exe
  • %Windows%\win32.exe
  • %Windows%\nvsvc32.exe
  • %User Temp%\drweb.exe
  • %User Temp%\win16.exe

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

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer
UserID = "1CCF4005EB3B638"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyEnable = "0"

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry value

[ 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.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRnyc = "%User Temp%\csrss.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRnyc = "%User Temp%\csrss.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRrse = "%User Temp%\svchost.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRrse = "%User Temp%\svchost.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRrvc = "%User Temp%\setup.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRrvc = "%User Temp%\setup.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKevc = "%Windows%\setup.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKevc = "%Windows%\setup.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRsPc = "%User Temp%\win32.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRsPc = "%User Temp%\win32.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKcuc = "%Windows%\lsass.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKcuc = "%Windows%\lsass.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRruf = "%User Temp%\spoolsv.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRruf = "%User Temp%\spoolsv.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRme = "%User Temp%\avp.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRme = "%User Temp%\avp.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKee = "%Windows%\user.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKee = "%Windows%\user.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKaoc = "%Windows%\debug.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKaoc = "%Windows%\debug.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRptc = "%User Temp%\msmgm.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRptc = "%User Temp%\msmgm.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRpuc = "%User Temp%\lsass.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRpuc = "%User Temp%\lsass.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKfre = "%Windows%\wininst.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKfre = "%Windows%\wininst.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKfPc = "%Windows%\win32.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKfPc = "%Windows%\win32.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MKdw+ = "%Windows%\nvsvc32.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MKdw+ = "%Windows%\nvsvc32.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRnsc = "%User Temp%\drweb.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRnsc = "%User Temp%\drweb.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRsPc = "%User Temp%\win16.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HNUGROXRsPc = "%User Temp%\win16.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
    • UserID = "1CCF4005EB3B638"

Step 4

Restore this modified registry value

[ 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.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • ProxyEnable = "0"

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_AGENT_024943.TOMB. 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 6

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\yawghd72y7huhd.tmp
  • %User Temp%\csrss.exe
  • %User Temp%\svchost.exe
  • %User Temp%\setup.exe
  • %Windows%\setup.exe
  • %User Temp%\win32.exe
  • %Windows%\lsass.exe
  • %User Temp%\spoolsv.exe
  • %User Temp%\avp.exe
  • %Windows%\user.exe
  • %Windows%\debug.exe
  • %User Temp%\msmgm.exe
  • %User Temp%\lsass.exe
  • %Windows%\wininst.exe
  • %Windows%\win32.exe
  • %Windows%\nvsvc32.exe
  • %User Temp%\drweb.exe
  • %User Temp%\win16.exe


Did this description help? Tell us how we did.