This page shows details and results of our analysis on the malware Downloader-ACC

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Threat Detail

  • Malware Type: Trojan
  • Malware Sub-type: Downloader
  • Protection Added: 2005-06-20

This is a trojan detection. Unlike viruses, trojans do not self-replicate. They are spread manually, often under the premise that they are beneficial or wanted. The most common installation methods involve system or security exploitation, and unsuspecting users manually executing unknown programs. Distribution channels include email, malicious or hacked web pages, Internet Relay Chat (IRC), peer-to-peer networks, etc.

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Malware Proliferation

Downloaders are designed to pull files from a remote website and execute the files that have been downloaded. As it is trivial for the malware author to modify the Downloader to refer to a different website or web address, McAfee write detection routines for Downloaders which as a general rule do not include these strings in the detection routines. This allows McAfee to write more generic detections for these threats and to proactively protect customers against future minor variants.

Therefore it is not possible to guarantee which website and/or port is being communicated with.

Also, as the website being communicated is normally controlled by the malware author, any files being downloaded can be remotely modified and the behaviour of these new binaries altered - possibly with every user infection.

This downloader is a browser helper object which monitors user internet browsing activity.  When Internet Explorer is launched and this BHO is installed, it will attempt to download a number of files to the local system.  In testing, the downloaded items replace the search agent for windows or may be installed as other browser helper objects.

System Changes

Files Added

  • javazk32.dll (122 KB)


The following registry keys are created:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
    Explorer\Browser Helper Objects\{F76A71DB-60E3-E66C-2F6C-D1E63E70622A}
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Explorer\Browser Helper Objects\{F76A71DB-60E3-E66C-2F6C-D1E63E70622A}
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\URLSearchHooks
  • HKEY_CLASSES_ROOT\CLSID\{F76A71DB-60E3-E66C-2F6C-D1E63E70622A}
    \InprocServer32\ "(default)"="javazk32.dll"
  • HKEY_CLASSES_ROOT\CLSID\{F76A71DB-60E3-E66C-2F6C-D1E63E70622A}\*

Many of these Downloaders install other malware including viruses as well as other Trojans.

Additionally many of them are used to remotely install Adware packages onto the affected host machine for the purposes of gaining referral revenue from the Adware software vendor.

Please note: If Adware is installed via a Downloader it may install it "cleanly" with the relevant uninstaller included for the user to terminate this Adware, although frequently this is not the case.

N/A. Downloaders are not viruses, and as such do not themselves contain any method to replicate. However they may themselves be downloaded by other viruses and/or Trojans to be installed on the user's system.

Many of these additionally are mass spammed by the author to entice people into double-clicking on them.

Alternatively they may be installed by visiting a malicious web page (either by clicking on a link, or by the website hosting a scripted exploit which installs the Downloader onto the user's system with no user interaction.

All Users:
Use current engine and DAT files for detection and removal.

Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).

But in some particular cases, the following steps need to be taken.

Please go to the Microsoft Recovery Console and restore a clean MBR.

On Windows XP:

  • Insert the Windows XP CD into the CD-ROM drive and restart the computer.
  • When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
  • Select the Windows installation that is compromised and provide the administrator password.
  • Issue 'fixmbr' command to restore the Master Boot Record
  • Follow onscreen instructions.
  • Reset and remove the CD from CD-ROM drive.

On Windows Vista and 7:

  • Insert the Windows CD into the CD-ROM drive and restart the computer.
  • Click on "Repair Your Computer".
  • When the System Recovery Options dialog comes up, choose the Command Prompt.
  • Issue 'bootrec /fixmbr' command to restore the Master Boot Record.
  • Follow onscreen instructions.
  • Reset and remove the CD from CD-ROM drive.