Analysis by: Christopher Daniel So
ALIASES:

VirTool:Win32/DelfInject.gen!AA (Microsoft), Trojan-Downloader.Win32.Agent.nrg (Kaspersky)

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

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 83,968 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 18 Jun 2011
Payload: Connects to URLs/IPs

Arrival Details

This Trojan may be dropped by other malware.

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

Installation

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

  • %System%\vistaupgrade.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
VistaUpgrade = "%System%\vistaupgrade.exe"

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.210.29:4545

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 8.232.02
FIRST VSAPI PATTERN DATE: 18 Jun 2011
VSAPI OPR PATTERN File: 8.233.00
VSAPI OPR PATTERN Date: 19 Jun 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

Scan your computer with your Trend Micro product and note files detected as TROJ_AGENT.AZZE

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete the file detected as TROJ_AGENT.AZZE

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 5

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\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • VistaUpgrade="%System%\vistaupgrade.exe"

Step 6

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