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Win32/Ursnif


Win32/Ursnif is a family of trojans that steals sensitive information from an affected machine.


What to do now

Manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as the Microsoft Safety Scanner (http://go.microsoft.com/fwlink/?LinkId=212742). For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.

Threat behavior

Win32/Ursnif is a family of trojans that steals sensitive information from an affected machine.
Installation
When executed, variants of Win32/Ursnif copy themselves to the following location:
%windir%\9129837.exe
They modify the registry to execute this copy at each Windows start:
Adds value: "ttool"
With data: "%windir%\9129837.exe"
To subkey HKCU\Software\Microsoft\Windows\CurrentVersion\Run
 
The trojan then executes its copy and drops and runs a batch file which deletes the original executable.
 
When the copy in the Windows directory is run, it drops and installs the driver "%windir%\new_drv.sys". This component is detected as VirTool/WinNT/Ursnif and is used to provide stealth (see Payload section below for further detail).
Payload
Steals Sensitive Information
Win32/Ursnif uses several methods in order to compromise the integrity of an affected machine's data. It attempts to steal sensitive data both in transit and in storage, and targets the following:
 
  • Clear text passwords in transit
    The trojan attempts to steal clear text passwords transmitted over the network. The trojan listens to all network traffic on every interface on a given machine, checking if it contains strings from common protocols that transmit passwords in clear text - for example FTP, POP3, IMAP and TELNET. If found the stolen data is posted to a remote location.
  • Protected Storage 
    The trojan attempts to steal passwords and credentials that are stored using protected storage.
  • Certificate Store 
    Ursnif attempts to steal Certificates and Private Keys from the Certificate store.
  • Running Processes
    Ursnif variants inject code into running processes that patches the following APIs to redirect to its own code:
    CreateProcessA
    CreateProcessW
    InternetReadFile         
    HttpSendRequestA         
    HttpSendRequestW         
    InternetReadFileExA      
    InternetReadFileExW      
    InternetCloseHandle      
    InternetQueryDataAvailable

    It does this to inspect and steal any relevant information passed to these APIs and to inject its own code into any newly created process. The stolen information is then posted to a remote site
 
Opens Socks Proxy
The trojan sets up a socks proxy on a random port. Proxy servers may be used by attackers in order to hide the origin of malicious activity. The port information is posted to a remote host.
 
Update Functionality
Win32/Ursnif allows unauthorized access to an affected machine. The trojan connects to a remote host with version information. When passed a parameter in response to the version information sent, it removes any currently running versions of the trojan before installing an updated version of itself (should a newer version be available from the remote host).
 
Provides Stealth
Variants of Win32/Ursnif drop a driver %windir%\new_drv.sys that is used to provide stealth to mask the files, registry entries and processes being used by the trojan. This component is detected as VirTool/WinNT/Ursnif.
 
Stops Services
The trojan stops the following services in an attempt to disable the firewall and other security-related services:
  • SharedAccess
  • wscsvc
Additional Information
Win32/Ursnif stores configuration data under the following registry entry:
HKCU\Software\Microsoft\InetData 
 
Analysis by Ray Roberts

Symptoms

System Changes
The following system changes may indicate the presence of this malware:
  • The presence of the following file:
    %windir%\9129837.exe
  • The presence of the following registry modification:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run
    ttool = "%windir%\9129837.exe"

Prevention

Take the following steps to help prevent infection on your system:
  • Enable a firewall on your computer.
  • Get the latest computer updates for all your installed software.
  • Use up-to-date antivirus software.
  • Use caution when opening attachments and accepting file transfers.
  • Use caution when clicking on links to web pages.
  • Protect yourself against social engineering attacks.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.
To turn on the Windows Firewall in Windows Vista
  1. Click Start, and click Control Panel.
  2. Click Security.
  3. Click Turn Windows Firewall on or off.
  4. Select On.
  5. Click OK.
To turn on the Internet Connection Firewall in Windows XP
  1. Click Start, and click Control Panel.
  2. Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
  3. Click Change Windows Firewall Settings.
  4. Select On.
  5. Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor websites.
 
You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows Vista
  1. Click Start, and click Control Panel
  2. Click System and Maintainance.
  3. Click Windows Updates.
  4. Select a setting. Microsoft recommends selecting Install updates automatically and choose a time that is convenient for you. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
To turn on Automatic Updates in Windows XP
  1. Click Start, and click Control Panel
  2. Click System.
  3. Click Automatic Updates.
  4. Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.
Use caution when opening attachments and accepting file transfers
Exercise caution with e-mail and attachments received from unknown sources, or received unexpectedly from known sources.  Use extreme caution when accepting file transfers from known or unknown sources.
Use caution when clicking on links to web pages
Exercise caution with links to web pages that you receive from unknown sources, especially if the links are to a web page that you are not familiar with or are suspicious of. Malicious software may be installed in your system simply by visiting a web page with harmful content.
Avoid downloading pirated software
Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information. please see our article 'The risks of obtaining and using pirated software'.
Protect yourself from social engineering attacks
While attackers may attempt to exploit vulnerabilities in hardware or software in order to compromise a system, they also attempt to exploit vulnerabilities in human behavior in order to do the same. When an attacker attempts to take advantage of human behavior in order to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted system. For more information, please see our article 'What is social engineering?'.

Alert level: Severe
This entry was first published on: Mar 31, 2009
This entry was updated on: Feb 04, 2013

This threat is also detected as:
  • Gozi (other)