TROJ_SCAR.AAS

October 09, 2012
 Analysis by: Michael Cabel
 Modified by: Kathleen Notario
 ALIASES:

Trojan.Gen.2 (Symantec); Trojan:Win32/Orsam!rts (Microsoft); Trojan.Win32.Scar.fcfu (Kaspersky); Generic BackDoor.un (Mcafee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

It connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

16,384 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 Nov 2011

Payload:

Steals information

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 Profile%\y1ag2rtq9f.exe
  • %User Profile%\7pyftc21y9.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It adds the following processes:

  • svchost.exe

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • y1ag2rtq9f
  • 7pyftc21y9

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
y1ag2rtq9f = "%User Profile%\y1ag2rtq9f.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
7pyftc21y9 = %User Profile%\7pyftc21y9.exe

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
y1ag2rtq9f = {hex value}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
7pyftc21y9 = {hex value}

Other Details

This Trojan connects to the following website to send and receive information:

  • {BLOCKED}.{BLOCKED}.181.242
  • {BLOCKED}.{BLOCKED}.181.243
  • {BLOCKED}.{BLOCKED}.181.244
  • {BLOCKED}.{BLOCKED}.254.226
  • {BLOCKED}.{BLOCKED}.254.108
  • {BLOCKED}.{BLOCKED}.254.109
  • {BLOCKED}rt.in
  • abc.{BLOCKED}rt.in
  • {BLOCKED}an.com
  • www.{BLOCKED}an.com
  • mail.{BLOCKED}an.com
  • mx.{BLOCKED}an.com

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

NOTES:

It injects codes into its created process svchost.EXE.

It attempts to send spammed emails received from above mentioned remote sites using the following servers:

  • alt4.gmail-smtp-in.l.google.com
  • gmail-smtp-in.l.google.com
  • in1.smtp.messagingengine.com
  • mail7.digitalwaves.co.nz
  • mxs.mail.ru

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.574.08

FIRST VSAPI PATTERN DATE:

15 Nov 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

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
    • y1ag2rtq9f = "%User Profile%\y1ag2rtq9f.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • 7pyftc21y9 = %User Profile%\7pyftc21y9.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • y1ag2rtq9f = {hex value}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • 7pyftc21y9 = {hex value}

Step 4

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