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Threat Encyclopedia

PE_VIRUX.AA

ANALYSIS BY

Roland Marco Dela Paz


ALIASES:

W32.Virut.CF, Virus:Win32/Virut.BN

PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type:File infector

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW


This file infector may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

TECHNICAL DETAILS

File Size:

Varies

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

12 Jul 2010

Arrival Details

This file infector may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This file infector injects codes into the following process(es):

  • WINLOGON.EXE

Other System Modifications

This file infector creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
\??\%System%\winlogon.exe = \??\%System%\winlogon.exe:*:enabled:@shell32.dll,-1

File Infection

This file infector infects the following file types:

  • .EXE
  • .SCR

It avoids infecting files that contain the following strings in their names:

  • OTSP
  • WC32
  • WCUN
  • WINC

It avoids infecting the following files:

  • .DLL files
  • PE Files with "_win" section name
  • Files with infection marker

HOSTS File Modification

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

  • 127.0.0.1 {BLOCKED}L.chura.pl

Other Details

Based on analysis of the codes, it has the following capabilities:

  • Connects to any of the following IRC servers using port 80:
    • {BLOCKED}c.zief.pl
    • {BLOCKED}m.ircgalaxy.pl
  • Connects to the said servers using 8-randomly generated character for its NICK and 1-randomly generated character for its USER. Once connected, it joins a certain channel to receive and execute commands on the affected system. As of this writing, the servers reply with a command to download the following file:
    • http://{BLOCKED}a.com/kb9.txt - detected by Trend Micro as TROJ_DLOAD.JKZQ
    This file is saved as temp files in %User Temp% folder. This file infector then executes the downloaded file. As a result, malicious routines of the downloaded file are exhibited on the affected system.
  • Performs DNS request to the following site which is inaccessible as of writing:
    • {BLOCKED}ns.pl
  • Hooks the following APIs so that when these APIs are called, the malware code is executed which then infects files:
    • NtCreateFile
    • NtOpenFile
    • NtCreateProcess
    • NtCreateProcessEx
    • NtQueryInformationProcess
  • Infects script files by first checking if the target script file's extension name is any of the following:.
    • ASP
    • .HTM
    • .PHP
  • Once it finds target script files, it creates a flag for the file for iFrame infection. It opens flagged files, then checks for a certain string in the file. If it finds that string, it skips the file. If not, then it proceeds with the infection of the file.
  • Looks for the string < /BODY > in the target script file. Once found, it infects script files by inserting the malicious IFRAME code below:
    Infected script files are detected as HTML_IFRME.QAWA. Trend Micro detects the infected files (EXE/SCR) as either PE_VIRUX.J, PE_VIRUX.N-3, and PE_VIRUX.AA.
  • Returns execution to the HOST file's original code after execution of its routines.

SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.300.06

FIRST VSAPI PATTERN DATE:

12 Jul 2010

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

AUTOMATIC REMOVAL INSTRUCTIONS

To automatically remove this malware from your system, use Trend Micro's special fixtool. Download, extract, and run the said fixtool in the same folder where your latest Trend Micro pattern file is located. For more details, refer to the fixtool's incorporated text file.

MANUAL REMOVAL INSTRUCTIONS

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • \??\%System%\winlogon.exe = \??\%System%\winlogon.exe:*:enabled:@shell32.dll,-1

Step 5

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

[ Learn More ]
    127.0.0.1 {BLOCKED}L.chura.pl
"

Step 6

Scan your computer with your Trend Micro product to clean files detected as PE_VIRUX.AA. 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 7

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