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Win32/Kelihos


Win32/Kelihos is a trojan family that distributes spam email messages. The spam messages could contain hyperlinks to installers of Win32/Kelihos malware. The malware may communicate with remote servers to exchange information that is used to execute various tasks, including sending spam email, capturing sensitive information or downloading and executing arbitrary files.



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/Kelihos is a trojan family that distributes spam email messages. The spam messages could contain hyperlinks to installers of Win32/Kelihos malware. The malware may communicate with remote servers to exchange information that is used to execute various tasks, including sending spam email, capturing sensitive information or downloading and executing arbitrary files.

Installation

When run, Win32/Kelihos creates a shared memory object, or "section object", named "GoogleImpl" to ensure only one instance of the trojan executes at a time. The registry is modified to run Win32/Kelihos at each Windows start:

In subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Sets value: "SmartIndex"
With data: "<path and file name of Win32/Kelihos trojan>"

Some variants may also install WinPcap, a legitimate and commonly used Windows packet capture library, as the following files:

  • <system folder>\packet.dll
  • <system folder>\wpcap.dll
  • <system folder>\drivers\npf.sys

These files are not malicious themselves, but Kelihos uses them to spy on the affected computer’s network activities.

Payload

Communicates with a remote host
Win32/Kelihos exchanges encrypted messages with a remote server via HTTP protocol (TCP 80) to evade detection by security software or other filters. Some variants of the malware use a crafted User-Agent from the following list when communicating with the remote host:

  • Mozilla/5.0 (Windows; U; Windows NT 6.1; ja; rv:1.9.2a1pre) Gecko/20090403 Firefox/3.6a1pre
  • Mozilla/5.0 (X11; U; Linux x86_64; cy; rv:1.9.1b3) Gecko/20090327 Fedora/3.1-0.11.beta3.fc11 Firefox/3.1b3
  • Mozilla/5.0 (Windows; U; Windows NT 5.1; es-AR; rv:1.9.0.11) Gecko/2009060215 Firefox/3.0.11
  • Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_6 ; nl; rv:1.9) Gecko/2008051206 Firefox/3.0
  • Mozilla/5.0 (Windows; U; Windows NT 6.1; es-AR; rv:1.9) Gecko/2008051206 Firefox/3.0
  • Mozilla/5.0 (Windows; U; Windows NT 5.1; pt-BR; rv:1.8.1.15) Gecko/20080623 Firefox/2.0.0.15
  • Mozilla/5.0 (Windows; U; Windows NT 6.0; zh-HK; rv:1.8.1.7) Gecko Firefox/2.0
  • Mozilla/5.0 (Windows; U; Win95; it; rv:1.8.1) Gecko/20061010 Firefox/2.0
  • Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8.0.7) Gecko/20060909 Firefox/1.5.0.7
  • Mozilla/5.0 (ZX-81; U; CP/M86; en-US; rv:1.8.0.1) Gecko/20060111 Firefox/1.5.0.1
  • Mozilla/5.0 (X11; U; NetBSD alpha; en-US; rv:1.8) Gecko/20060107 Firefox/1.5
  • Mozilla/5.0 (Windows; U; Windows NT 5.2; en-US; rv:1.8b5) Gecko/20051006 Firefox/1.4.1
  • Mozilla/5.0 (X11; I; SunOS sun4u; en-GB; rv:1.7.8) Gecko/20050713 Firefox/1.0.4
  • Mozilla/5.0 (X11; U; Linux i686; de-AT; rv:1.7.5) Gecko/20041222 Firefox/1.0 (Debian package 1.0-4)
  • Mozilla/5.0 (Windows; U; Win 9x 4.90; rv:1.7) Gecko/20041103 Firefox/0.9.3
  • Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; fr; rv:1.7) Gecko/20040624 Firefox/0.9
  • Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; FDM; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 1.1.4322)
  • Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET CLR 1.1.4322; Tablet PC 2.0; OfficeLiveConnector.1.3; OfficeLivePatch.1.3; MS-RTC LM 8; InfoPath.3)
  • Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; .NET CLR 3.0.04506; .NET CLR 1.1.4322; InfoPath.2; .NET CLR 3.5.21022)
  • Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322)
  • Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; Win64; x64; SV1)
  • Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30)
  • Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
  • Mozilla/4.0 (compatible; MSIE 5.5; Windows 95)
  • Mozilla/4.0 (compatible; MSIE 4.01; Windows NT 5.0)
  • Mozilla/2.0 (compatible; MSIE 3.0; Windows 3.1)
  • Mozilla/1.22 (compatible; MSIE 1.5; Windows NT)
  • Microsoft Internet Explorer/1.0 (Windows 95)

Data received from the remote server is interpreted by Win32/Kelihos and could contain instructions for the malware to perform any number of actions, including but not limited to the following:

  • Update a list of possibly compromised computers that the malware communicates and exchanges information with
  • Send spam email messages
  • Capture sensitive information
  • Send notifications or reports
  • Download and execute arbitrary files

Sends spam
Win32/Kelihos uses SMTP to send spam email messages that are constructed based on certain templates and other data received from a remote server. The subject, body and contents of the spam email vary and can be updated at any time.Win32/Kelihos may have more than one spam campaign running at the same time. Win32/Kelihos may harvest email addresses from the affected computer's local drive by searching within certain files. It avoids searching within certain file types, including the following:

  • .7z
  • .avi
  • .bmp
  • .class
  • .dll
  • .exe
  • .gif
  • .gz
  • .hxd
  • .hxh
  • .hxn
  • .hxw
  • .jar
  • .jpeg
  • .jpg
  • .mov
  • .mp3
  • .msi
  • .ocx
  • .ogg
  • .png
  • .rar
  • .vob
  • .wav
  • .wave
  • .wma
  • .wmv
  • .zip

The harvested email addresses are used as potential recipients for spam email messages distributed by Win32/Kelihos.

Captures sensitive information
Variants of Win32/Kelihos may use WinPcap to monitor network traffic and capture information such as login credentials from FTP, POP3 and SMTP traffic. In addition, Kelihos checks for the presence of the following applications in the affected computer and attempts to steal login credentials, digital currency and other information:

  • 32-bit FTP
  • Bitcoin
  • BitKinex
  • Bullet Proof FTP
  • BulletProof FTP Client
  • Classic FTP
  • Core FTP
  • CoreFTP
  • CuteFTP
  • Directory Opus
  • FAR Manager
  • FFFTP
  • FTP Commander
  • FTP Commander Deluxe
  • FTP Commander Pro
  • FTP Control
  • FTP Explorer
  • FTP Navigator
  • FTPRush
  • FileZilla
  • FlashFXP
  • Fling
  • Fling FTP
  • Frigate3
  • Frigate3 FTP
  • LeapFTP
  • NetDrive
  • SecureFX
  • SmartFTP
  • SoftX FTP Client
  • Sota FFFTP
  • Total Commander
  • TurboFTP
  • UltraFXP
  • WS_FTP
  • WebDrive
  • WebSitePublisher
  • WinSCP

Analysis by Gilou Tenebro


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. For more information, see 'What is social engineering?'.

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/protect/yourself/password/create.mspx.

 

Alert level: Severe
This entry was first published on: Sep 22, 2011
This entry was updated on: Sep 29, 2011

This threat is also detected as:
  • Hlux botnet (Kaspersky)