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WORM_KELIHOS.YVI

January 06, 2016
 Analysis by: RonJay Kristoffer Caragay
 ALIASES:

Backdoor:Win32/Kelihos (Microsoft); Backdoor.Win32.Hlux.fite (Kaspersky); Mal/Kelihos-D (Sophos);

 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:

Copies itself in all available physical drives, Propagates via removable drives, Downloaded from the Internet


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

  TECHNICAL DETAILS

File Size:

1,121,657 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Dec 2015

Payload:

Steals information

Arrival Details

This backdoor arrives via removable drives.

It 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 the following copies of itself into the affected system and executes them:

  • {existing directory}\{random filename}.exe → detected as WORM_KELIHOS.YVI as well
    where it drops itself into an existing directory using any of the following filename:
    • acrord32
    • agent
    • alg
    • ati2evxx
    • avguard
    • batch
    • block
    • ccapp
    • ccevtmgr
    • ccsetmgr
    • convert
    • decompile
    • defwatch
    • dit
    • download
    • dwm
    • edit
    • em_exec
    • explorer
    • extract
    • ezsp_px
    • file
    • firefox
    • fix
    • gearsec
    • hkcmd
    • hkcr
    • htpatch
    • ielowutil
    • ieuser
    • iexplore
    • igfxtray
    • install
    • isuspm
    • java
    • jqs
    • jucheck
    • jusched
    • khalmnpr
    • klwtblfs
    • lame
    • launch
    • lsass
    • lucoms
    • mac
    • mcshield
    • mcvsescn
    • msascui
    • mscorsvw
    • mspmspsv
    • naprdmgr
    • navapsvc
    • nprotect
    • ntvdm
    • nvsvc32
    • nvxdsync
    • nwiz
    • open
    • pctspk
    • pdvddxsrv
    • play
    • point32
    • qbw32
    • qttask
    • rename
    • run
    • rundll32
    • services
    • setup
    • sidebar
    • smc
    • spoolsv
    • svchost
    • taskman
    • terraria
    • toaster
    • trustedinstaller
    • unhide
    • unpack
    • unzip
    • update
    • upgrade
    • uptime
    • view
    • vsmon
    • webscanx
    • winlogon
    • wisptis
    • wmpnetwk
    • wmpnscfg
    • xsd
    • zcfgsvc
    • zip
    • zumodrive

It drops the following files:

  • {malware path}\tmp.exe ← deleted afterwards

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
{random parameter 1}{random parameter 2} = "{malware path and file name}"

Propagation

This backdoor drops the following copies of itself in all physical and removable drives:

  • {Removable Drive Letter}:\{filename}.exe
    where {filename} can be any of the following:
    • password
    • screensaver
    • click
    • installer
    • hentai
    • install
    • run
    • setup
    • porn
    • game

Backdoor Routine

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

  • http://{random generated IP addresses}/{variable}.htm
    where {variable} can be any of the following:
    • file
    • online
    • main
    • start
    • install
    • login
    • setup
    • welcome
    • search
    • home
    • default
    • index

Dropping Routine

This backdoor drops the following files:

  • This worm installs WinPcap, a legitimate and commonly used Windows packet capture library used to monitor the infected computer's network activities, by dropping and installing the following non-malicious files:
    • %System%\packet.dll
    • %System%\wpcap.dll
    • %System%\drivers\npf.sys

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Information Theft

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

  • 32BitFtp
  • 3DFTP
  • ALFTP
  • BitKinex
  • BlazeFtp
  • BPFTP
  • BulletProof FTP
  • COREFTP
  • CUTEFTP
  • Classic FTP
  • Core FTP
  • CuteFTP
  • DeluxeFTP
  • Directory Opus
  • EasyFTP
  • FAR Manager FTP
  • FFFTP
  • FTP Commander Deluxe
  • FTP Commander Pro
  • FTP Explorer
  • FTP Navigator
  • FTP Now
  • FTP Surfer
  • FTP++
  • FTPGetter
  • FTPRush
  • FTPWare
  • Frigate3 FTP
  • GPSoftware
  • GoFTP
  • Ipswitch
  • LEAPFTP
  • LeechFTP
  • P32bit FTP
  • SmartFTP
  • SoftX FTP
  • Staff-FTP
  • TurboFTP
  • WS_FTP
  • WinFTP
  • XFTP
  • FileZilla
  • SecureFX
  • FlashFXP
  • UltraFXP
  • FreshFTP
  • Cyberduck
  • FTP Shell
  • TFTPInfo

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

  • FTP User Name
  • FTP Password
  • FTP Server Name
  • Port Number

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

  • Chrome
  • Chromium
  • ChromePlus
  • Bromium
  • Nichrome
  • Comodo
  • RockMelt
  • CoolNovo
  • ChromePlus
  • Yandex

Other Details

This backdoor drops the following file(s)/component(s):

  • {Removable Drive Letter}:\Shortcut to {filename}.lnk ← shortcut link pointing to the malware copy

It does the following:

  • Modifies its file attributes to Read-only and Hidden after execution.
  • 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)
  • Attempts to steal information from the file %Application Data%\Bitcoin\wallet.dat
  • Monitors network traffic to acquire data from email and FTP accounts using the following strings:
    • @
    • AUTH
    • Authorization
    • Basic
    • CONNECT
    • ftp
    • http
    • PASS
    • PLAIN
    • pop3
    • pop3_smtp
    • PUT
    • smtp
    • USER
  • Creates .LNK (shortcut) files using folder names found in removable drives. It then hides the original folders tricking users to click .LNK files. This .LNK files point out to a dropped copy of itself in the removable drive.

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on 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.)

NOTES:

The autorun registry {random parameter 1} may be any of the following:

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

The autorun registry {random parameter 2} may be any of the following:

  • Informer
  • Verifyer
  • Saver
  • Notifyer
  • Checker
  • Updater

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.240.03

FIRST VSAPI PATTERN DATE:

29 Dec 2015

VSAPI OPR PATTERN File:

12.241.00

VSAPI OPR PATTERN Date:

30 Dec 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
    • {random parameter 1}{random parameter 2} = "{malware path and file name}"

Step 5

Search and delete these files

[ 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.
  • {malware path}\tmp.exe
  • {Removable Drive Letter}:\Shortcut to {filename}.lnk

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_KELIHOS.YVI. 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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