Risk Level 1: Very Low

Discovered: September 20, 2010
Updated: September 20, 2010 10:40:15 AM
Type: Trojan
Infection Length: 758,272 or 790,016 bytes
Systems Affected: Windows 98, Windows 95, Windows XP, Windows Me, Windows Vista, Windows NT, Windows Server 2003, Windows 2000


Infostealer.Nimkey is a Trojan horse that gathers private key certificates, keystrokes, and clipboard data and sends it to a predetermined website.

Antivirus Protection Dates

  • Initial Rapid Release version September 20, 2010 revision 009
  • Latest Rapid Release version September 20, 2010 revision 019
  • Initial Daily Certified version pending
  • Latest Daily Certified version pending
  • Initial Weekly Certified release date September 22, 2010

Threat Assessment


  • Wild Level: Low
  • Number of Infections: 0 - 49
  • Number of Sites: 0 - 2
  • Geographical Distribution: Low
  • Threat Containment: Easy
  • Removal: Easy


  • Damage Level: Medium
  • Payload: Sends gathered information to a predetermined website.
  • Releases Confidential Info: Gathers private key certificates, keystrokes, and clipboard data.


  • Distribution Level: Low


The Trojan may arrive as a file with one of the following file names:
  • %CurrentFolder%\irs-pdf-f941.irs.com
  • %CurrentFolder%\report6.com
  • %CurrentFolder%\details.com

When the Trojan is executed, it downloads a file from one of the following URLs and saves it as %Windir%\inf\alg.exe:
  • [http://]www.psbprzedborz.pl/[REMOVED]
  • [http://][REMOVED]
  • [http://][REMOVED]

It also downloads a file from one of the following URLs and saves it as %Windir%\inf\AcroIEHelper.dll:
  • [http://]www.psbprzedborz.pl/[REMOVED]
  • [http://][REMOVED]
  • [http://][REMOVED]

The Trojan then downloads a non-malicious file from one of the following URLs and saves it as
  • [http://]www.psbprzedborz.pl/ChilkatCe[REMOVED]
  • [http://][REMOVED]
  • [http://][REMOVED]

It also downloads another non-malicious file from one of the following URLs and saves it as
  • [http://]www.psbprzedborz.pl/extract_[REMOVED]
  • [http://][REMOVED]
  • [http://][REMOVED]

The Trojan then deletes the following files:
  • %Windir%\inf\netfxocm.cookies.PNF
  • %UserProfile%\Application Data\Mozilla\Firefox\Profiles\[PROFILE FOLDER]\cookies.txt
  • %UserProfile%\Application Data\Mozilla\Firefox\Profiles\[PROFILE FOLDER]\signons2.txt
  • %UserProfile%\Application Data\Mozilla\Firefox\Profiles\[PROFILE FOLDER]\history.dat
  • %UserProfile%\Application Data\Mozilla\Firefox\Profiles\[PROFILE FOLDER]\formhistory.dat

It also deletes all files in the following folder:

The Trojan creates the following registry subkeys:
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\{FCADDC14-BD46-408A-9842-CDBE1C6D37EB}

The Trojan creates a service with the following details:
Service Name: WSALG2
Description: Application Layer Gateway Service2

It creates the following subkey for the above service:

The Trojan also modifies the following registry entries:
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"TaskbarNoNotification" = "1"
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\"EnableBalloonTips" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\"EnableLUA" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\"ConsentPromptBehaviorAdmin" = "0"
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\"TaskbarNoNotification" = "1"
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\"EnableBalloonTips" = "0"

The Trojan records keystrokes, gathers clipboard data, and files that fit the following string:

It uploads any data found to the following URL:

The Trojan may download updates of itself.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.