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Win32/Dishigy


Win32/Dishigy is a family of trojans that can be instructed to perform denial of service attacks on remote hosts. The trojan attempts to connect to a remote host in order to obtain configuration information, and may be instructed to perform any one of several types of attacks.



What to do now

To detect and remove this threat and other malicious software that may be installed on your computer, run a full-system scan with an appropriate, up-to-date, security solution. The following Microsoft products detect and remove this threat:

For more information on antivirus software, see http://www.microsoft.com/windows/antivirus-partners/.

Threat behavior

Win32/Dishigy is a family of trojans that can be instructed to perform denial of service attacks on remote hosts. The trojan attempts to connect to a remote host in order to obtain configuration information, and may be instructed to perform any one of several types of attack.

Installation

When executed, the malware copies itself to one of the following locations:

  • <system folder> \drivers\ <file name>.exe 

For example:

    • <system folder> \drivers\wvchatts.exe
    • <system folder> \drivers\svajnager.exe
    • <system folder> \drivers\svflooje.exe
    • <system folder> \drivers\svchost.exe

  • <system folder> \<file name>.exe

For example:

    • <system folder> \svdhalp.exe

Note: <system folder> refers to a variable location that is determined by the malware by querying the operating system. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP, Vista, and 7 is C:\Windows\System32.

Win32/Dishigy may also set itself to run as a service, to ensure that it runs each time Windows starts.

The malware can also create the following file:

%windir%\keys.ini

This file contains a randomly generated string which it uses to uniquely identify itself.

Payload

Performs Denial of Service attacks

When executed, the trojan attempts to connect to a remote host to receive configuration data. The configuration provides the following information:

  • The type of attack to be performed
    • Noting that early variants of the malware were capable of performing only a single type, this was expanded with later variants
    • Including sending a large number of HTTP requests to a targeted host
    • Depending on the type of attack, this determines the type of request sent
  • The intensity of an attack. That is, the resources of an infected computer that should be used to target a given host
  • The duration of an attack
  • A list of targeted hosts to perform a denial of service attack on

Once the configuration data is received, the malware then proceeds to perform attacks against the given list of hosts.

Technical details: The type of requests may include HTTP GET requests and HTTP POST requests.

The malware may include a variety of HTTP header information, including a randomly chosen USER-Agent string from a list which it carries, as well as a randomly chosen "Referrer URL", also from a list it carries.

Analysis by Ray Roberts


Symptoms

There are no common symptoms associated with this threat. Alert notifications from installed antivirus software may be the only symptoms.


Prevention

Take the following steps to help prevent infection on your computer:
  • Enable a firewall on your computer.
  • Get the latest computer updates for all your installed software.
  • Use up-to-date antivirus software.
  • Limit user privileges on the computer.
  • Use caution when opening attachments and accepting file transfers.
  • Use caution when clicking on links to webpages.
  • Avoid downloading pirated software.
  • Protect yourself against social engineering attacks.
  • Use strong passwords.
Enable a firewall on your computer

Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.

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. Instructions on how to download the latest versions of some common software is available from the following:

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.

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, such as Microsoft Security Essentials, that is updated with the latest signature files. For more information, see http://www.microsoft.com/windows/antivirus-partners/.

Limit user privileges on the computer

Starting with Windows Vista and Windows 7, Microsoft introduced User Account Control (UAC), which, when enabled, allowed users to run with least user privileges. This scenario limits the possibility of attacks by malware and other threats that require administrative privileges to run.

You can configure UAC in your computer to meet your preferences:

Use caution when opening attachments and accepting file transfers

Exercise caution with email 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 webpages

Exercise caution with links to webpages that you receive from unknown sources, especially if the links are to a webpage that you are not familiar with, unsure of the destination of, or suspicious of. Malicious software may be installed in your computer simply by visiting a webpage 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, see '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 to compromise a computer, they also attempt to exploit vulnerabilities in human behavior to do the same. When an attacker attempts to take advantage of human behavior 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 computer.

Use strong passwords

Attackers may try to gain access to your Windows account by guessing your password. It is therefore important that you use a strong password – one that cannot be easily guessed by an attacker. A strong password is one that has at least eight characters, and combines letters, numbers, and symbols. For more information, see http://www.microsoft.com/security/online-privacy/passwords-create.aspx.


Alert level: Severe
This entry was first published on: May 04, 2012
This entry was updated on: May 07, 2012

This threat is also detected as:
No known aliases