Modified by: Pearl Charlaine Espejo
ALIASES:

Trojan.Win32.Crypt.ddf (Kaspersky); Backdoor:Win32/Kelihos (Microsoft); Mal/Kelihos-B (Sophos); Gen:Variant.Zusy.126166 (BitDefender); Trojan horse Crypt3.BZOZ (AVG)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 1,491,456 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 07 Feb 2015
Payload: Sends messages, Compromises network security, Steals information

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops and executes the following files:

  • %Desktop%\tmp.exe

(Note: %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
NetworkInformer = "{malware path and file name}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Request spam email messages structure and template
  • Send spam email messages
  • Send stolen information
  • Get operating system information
  • Get drive information
  • List running processes
  • Download and execute arbitrary files
  • Update server with a list of compromised computers
  • Manage registry
  • Download updated copy of itself

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {random IP addresses}

Information Theft

This backdoor gathers the following data:

  • Network traffic information
  • Login credentials from FTP, POP3 and SMTP traffic
  • Bitcoins

It attempts to steal stored account information used in the following installed File Transfer Protocol (FTP) clients or file manager software:

  • 32bit FTP
  • 3DFTP
  • ALFTP
  • BitKinex
  • Blaze
  • BulletProof
  • Classic FTP
  • CoffeeCup
  • Core FTP
  • CuteFTP
  • CyberDuck
  • Deluxe
  • Directory Opus
  • ExpanDrive
  • FFFTP
  • FileZilla
  • FlashFXP
  • FreeFTP/DirectFTP
  • Frigate3
  • FTP Control
  • FTP Explorer
  • FTPGetter
  • FTPRush
  • Global Downloader
  • IE
  • LeapFTP
  • Leech
  • Linas
  • MyFTP
  • NetDrive
  • NetFile
  • Nexus
  • Notepad++
  • NovaFTP
  • Putty
  • Robo
  • SecureFX
  • Sherrod
  • SmartFTP
  • SoftX FTP Client
  • Staff
  • TFTPInfo
  • Total Commander
  • TurboFTP
  • WebDrive
  • WebSitePublisher
  • Whisper/Surfer
  • WinSCP
  • WISE
  • XFTP

It gathers the following account information from any of the mentioned File Transfer Protocol (FTP) clients or file manager software:

  • Server Name
  • User Name
  • Password
  • Directory
  • Port

It attempts to get stored information such as user names, passwords, and hostnames from the following browsers:

  • Bromium
  • ChromePlus
  • Chromium
  • Comodo
  • CoolNovo
  • Epic Browser
  • Flock Browser
  • Google Chrome
  • K-Meleon
  • Mozilla Firefox
  • MozSuite
  • Nichrome
  • RockMelt
  • SeaMonkey
  • Yandex

NOTES:

This backdoor modifies its file attributes to Read-only and Hidden after execution.

The auto-run registry, {random parameter 1} can be any of the following:

  • Network
  • Time
  • CrashReport
  • Database
  • Icon
  • Desktop
  • Tray
  • Video
  • Media

The auto-run registry, {random parameter 2} can be any of the following:

  • Checker
  • Informer
  • Notifyer
  • Saver
  • Updater
  • Verifyer
  • For example:
  • NetworkVerifyer
  • TrayNotifyer
  • CrashReportUpdater

This backdoor uses peer-to-peer (P2) network communication to get the IP addresses to use then it adds the following web sources:

  • file.htm
  • main.htm
  • install.htm
  • setup.htm
  • search.htm
  • default.htm
  • online.htm
  • start.htm
  • login.htm
  • welcome.htm
  • home.htm
  • index.htm

It saves its updated copy using the following file names:

  • acrord32
  • agent
  • alg
  • ati2evxx
  • avguard
  • bar
  • batch
  • block
  • ccapp
  • ccevtmgr
  • ccsetmgr
  • convert
  • decompile
  • defwatch
  • dit
  • download
  • dwm
  • edit
  • em_exec
  • explorer
  • extract
  • ezsp_px
  • fire
  • fix
  • fox
  • gearsec
  • hkcmd
  • hkcr
  • htpatch
  • ielowutil
  • ieuser
  • iexplore
  • igfxtray
  • isuspm
  • java
  • jqs
  • jucheck
  • jusched
  • khalmnpr
  • klwtblfs
  • lame
  • launch
  • lsass
  • lucoms
  • mac
  • mcshield
  • mcvsescn
  • msascui
  • mscorsvw
  • mspmspsv
  • naprdmgr
  • navapsvc
  • nprotect
  • ntvdm
  • nvsvc32
  • nvxdsync
  • nwiz
  • pctspk
  • pdvddxsrv
  • play
  • point32
  • qbw32
  • qttask
  • rename
  • run
  • rundll32
  • services
  • side
  • smc
  • spoolsv
  • svchost
  • taskman
  • terraria
  • toaster
  • trustedinstaller
  • unhide
  • unpack
  • unzip
  • update
  • upgrade
  • uptime
  • view
  • vsmon
  • webscanx
  • winlogon
  • wisptis
  • wmpnetwk
  • wmpnscfg
  • xsd
  • zcfgsvc
  • zip
  • zumodrive

The downloaded files' folder depends on the Download backdoor command.

It uses WinPcap, a legitimate and commonly used Windows packet capture library, to monitor the infected computer's network activities. It does this by dropping and installing the following non-malicious files:

  • %System%\packet.dll
  • %System%\wpcap.dll
  • %System%\drivers\npf.sys

It exchanges encrypted messages with a remote server via HTTP protocol (TCP port 80). It uses the following crafted User-Agent when communicating with the remote host:

  • Mozilla/5.0 (Windows NT 5.1) Gecko/20100101 Firefox/14.0 Opera/12.0
  • Opera/9.80 (Windows NT 5.1; U; zh-sg) Presto/2.9.181 Version/12.00
  • Opera/9.80 (Windows NT 6.1; U; es-ES) Presto/2.9.181 Version/12.00
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.0) Opera 12.14
  • Mozilla/5.0 (Windows NT 6.0; rv:2.0) Gecko/20100101 Firefox/4.0 Opera 12.14
  • Opera/9.80 (Windows NT 6.0) Presto/2.12.388 Version/12.14
  • Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; da-dk) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1
  • Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_8; de-at) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1
  • Mozilla/5.0 (iPad; CPU OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko ) Version/5.1 Mobile/9B176 Safari/7534.48.3
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/534.55.3 (KHTML, like Gecko) Version/5.1.3 Safari/534.53.10
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/537.13+ (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2
  • Mozilla/5.0 (iPad; CPU OS 6_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10A5355d Safari/8536.25
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; chromeframe/12.0.742.112)
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; Media Center PC 6.0; InfoPath.3; MS-RTC LM 8; Zune 4.7)
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 7.1; Trident/5.0)
  • Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)
  • Mozilla/1.22 (compatible; MSIE 10.0; Windows 3.1)
  • Mozilla/4.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/5.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Macintosh; Intel Mac OS X 10_7_3; Trident/6.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/4.0; InfoPath.2; SV1; .NET CLR 2.0.50727; WOW64)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/5.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)
  • Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.0; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20130331 Firefox/21.0
  • Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20130401 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20130328 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20130401 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130330 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130331 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20130401 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.2; rv:21.0) Gecko/20130326 Firefox/21.0
  • Mozilla/5.0 (X11; Linux i686; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:21.0) Gecko/20100101 Firefox/21.0
  • Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:21.0) Gecko/20130331 Firefox/21.0
  • Mozilla/5.0 (Windows NT 6.1; rv:22.0) Gecko/20130405 Firefox/22.0
  • Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:22.0) Gecko/20130328 Firefox/22.0
  • Mozilla/5.0 (Windows NT 6.2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1464.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1467.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1468.0 Safari/537.36
  • Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.2 Safari/537.36
  • Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
  • Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; Acoo Browser 1.98.744; .NET CLR 3.5.30729)

This backdoor sends spam email messages using Simple Mail Transfer Protocol (SMTP) connection. It harvests email addresses from the affected computer's local drive.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 11.502.06
FIRST VSAPI PATTERN DATE: 18 Feb 2015
VSAPI OPR PATTERN File: 11.503.00
VSAPI OPR PATTERN Date: 19 Feb 2015

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • NetworkInformer = "{malware path and file name}"

Step 5

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Desktop%\tmp.exe

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_KELIHOS.KLP. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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