Analysis by: Nikko Tamana

ALIASES:

W32/Dorkbot.BAA!tr (Fortinet)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via removable drives

This worm 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.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 397,312 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 13 Aug 2013
Payload: Connects to URLs/IPs, Steals information, Compromises system security, Downloads files

Arrival Details

This worm 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 worm drops the following copies of itself into the affected system:

  • %User Profile%\Application Data\{random}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It injects threads into the following normal process(es):

  • explorer.exe
  • winlogon.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random} = "%User Profile%\Application Data\{random}.exe"

Propagation

This worm creates the following folders in all removable drives:

  • {Removable Drive}:\RECYCLER

It drops the following copy(ies) of itself in all removable drives:

  • {Removable Drive}:\RECYCLER\{random}.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[AutoRun]
;{garbage characters}
shellexecute=RECYCLER\{random}.exe
;{garbage characters}
icon=shell32.dll,7
;{garbage characters}
shell\open\command=RECYCLER\{random characters}.exe
;{garbage characters}
action=Open folder to view files
;{garbage characters}
shell\explore\command=RECYCLER\{random}}.exe
;{garbage characters}
useautoplay=1

It sends messages that contain links to sites hosting remote copies of itself using the following instant-messaging (IM) applications:

  • MSN Messenger
  • mIRC

Backdoor Routine

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

  • Block DNS
  • Create processes
  • Download other files
  • Insert iFrame tags into HTML files
  • Join an IRC channel
  • Log in to FTP sites
  • Perform Slowloris, UDP, and SYN flooding
  • Run Reverse Socks4 proxy server
  • Send MSN Messenger messages
  • Steal login credentials
  • Update itself
  • Visit a web site

It connects to the following websites to send and receive information:

  • {BLOCKED}8.com
  • {BLOCKED}1.com
  • {BLOCKED}4.com
  • {BLOCKED}arorz.com
  • ns1.{BLOCKED}f.net
  • {BLOCKED}.160.19
  • {BLOCKED}.160.22
  • {BLOCKED}.161.19
  • {BLOCKED}.161.22

Other Details

This worm connects to the following URL(s) to get the affected system's IP address:

  • http://api.wipmania.com/

NOTES:

It monitors the user's browsing activities. It gathers the user's login ID, password and email when the site accessed by the user contains the following strings:

  • *.moneybookers.*/*login.pl
  • *1and1.com/xml/config*
  • *4shared.com/login*
  • *:2082/login*
  • *:2083/login*
  • *:2086/login*
  • *:2222/CMD_LOGIN*
  • *FLN-Password=*
  • *LoginPassword=*
  • *Passwd=*
  • *Password=*
  • *TextfieldPassword=*
  • *alertpay.com/login*
  • *aol.*/*login.psp*
  • *bcointernacional*login*
  • *bebo.*/c/home/ajax_post_lifestream_comment
  • *bebo.*/c/profile/comment_post.json
  • *bebo.*/mail/MailCompose.jsp*
  • *bigstring.*/*index.php*
  • *clave=*
  • *depositfiles.*/*/login*
  • *dotster.com/*login*
  • *dyndns*/account*
  • *enom.com/login*
  • *facebook.*/ajax/*MessageComposerEndpoint.php*
  • *facebook.*/ajax/chat/send.php*
  • *facebook.*/login.php*
  • *fastmail.*/mail/*
  • *fileserv.com/login*
  • *filesonic.com/*login*
  • *freakshare.com/login*
  • *friendster.*/rpc.php
  • *friendster.*/sendmessage.php*
  • *gmx.*/*FormLogin*
  • *godaddy.com/login*
  • *google.*/*ServiceLoginAuth*
  • *hackforums.*/member.php
  • *hotfile.com/login*
  • *letitbit.net*
  • *login.live.*/*post.srf*
  • *login.yahoo.*/*login*
  • *loginUserPassword=*
  • *login_password=*
  • *mediafire.com/*login*
  • *megaupload.*/*login*
  • *members*.iknowthatgirl*/members*
  • *members.brazzers.com*
  • *moniker.com/*Login*
  • *namecheap.com/*login*
  • *netflix.com/*ogin*
  • *netload.in/index*
  • *officebanking.cl/*login.asp*
  • *oron.com/login*
  • *paypal.*/webscr?cmd=_login-submit*
  • *runescape*/*weblogin*
  • *screenname.aol.*/login.psp*
  • *secure.logmein.*/*logincheck*
  • *sendspace.com/login*
  • *service=youtube*
  • *signin.ebay*SignIn
  • *sms4file.com/*/signin-do*
  • *speedyshare.com/login*
  • *steampowered*/login*
  • *thepiratebay.org/login*
  • *torrentleech.org/*login*
  • *twitter.*/*direct_messages/new*
  • *twitter.*/*status*/update*
  • *twitter.com/sessions
  • *uploaded.to/*login*
  • *uploading.com/*login*
  • *vip-file.com/*/signin-do*
  • *vkontakte.ru/api.php
  • *vkontakte.ru/mail.php
  • *vkontakte.ru/wall.php
  • *webnames.ru/*user_login*
  • *what.cd/login*
  • *whcms*dologin*
  • *youporn.*/login*

It attempts to steal user credentials used in the following websites:

  • 1and1
  • 4shared
  • Alertpay
  • Bcointernacional
  • Bebo
  • BigString
  • Brazzers
  • Clave
  • Depositfiles
  • Dotster
  • DynDNS
  • Ebay
  • Email
  • FLN-Password
  • FLN-UserName
  • Facebook
  • Fastmail
  • Fileserve
  • Filesonic
  • Freakshare
  • Friendster
  • Gmail
  • Godaddy
  • Hackforums
  • Hotfile
  • IKnowThatGirl
  • Letitbit
  • LogMeIn
  • Mediafire
  • Megaupload
  • Message
  • Moneybookers
  • Moniker
  • Namecheap
  • Netflix
  • Netload
  • OfficeBanking
  • Passwd
  • PayPal
  • Runescape
  • Sendspace
  • Sms4file
  • Speedyshare
  • Steam
  • Thepiratebay
  • Torrentleech
  • Twitter
  • Uploaded
  • Uploading.com
  • Vip-file
  • Vkontakte
  • Webnames
  • Whatcd
  • Yahoo
  • YouPorn
  • YouTube

It may also prevent the user from using the following applications:

  • cmd.exe
  • ipconfig.exe
  • regedit.exe
  • regsvr32.exe
  • rundll32.exe
  • verclsid.exe

It drops shortcut (.LNK) files named after the folders found in the removable drives which points to the copy of itself in the removable drives.

The target property of the .LNK files is the following:

  • %windir%\system32\cmd.exe /c "start %cd%RECYCLER\{random}.exe &&%windir%\explorer.exe %cd%RSA

Then, it sets the folders' attribute to HIDDEN.

It propagates via the following social media networks:

  • Bebo (Comment, Message)
  • Friendster (Message, Comment, Shoutout, Chat)
  • Twitter (Tweet, Message)
  • Facebook (Message, Chat, Status)

It monitors if browser accesses URLs with following strings:

  • avast
  • avira
  • bitdefender
  • bullguard
  • clamav
  • comodo
  • emsisoft
  • eset
  • f-secure
  • fortinet
  • garyshood
  • gdatasoftware
  • heck.tc
  • iseclab
  • jotti
  • kaspersky
  • lavasoft
  • malwarebytes
  • mcafee
  • norman
  • norton
  • novirusthanks
  • nprotect
  • onecare.live
  • onlinemalwarescanner
  • pandasecurity
  • precisesecurity
  • sophos
  • sunbeltsoftware
  • symantec
  • threatexpert
  • trendmicro
  • virscan
  • virus
  • virusbuster
  • viruschief
  • virustotal
  • webroot

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.214.04
FIRST VSAPI PATTERN DATE: 13 Aug 2013
VSAPI OPR PATTERN File: 10.215.00
VSAPI OPR PATTERN Date: 14 Aug 2013

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

Scan your computer with your Trend Micro product and note files detected as WORM_DORKBOT.DCL

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random} = "%User Profile%\Application Data\{random}.exe"

Step 5

Search and delete AUTORUN.INF files created by WORM_DORKBOT.DCL that contain these strings

[ Learn More ]
[AutoRun]
;{garbage characters}
shellexecute=RECYCLER\{random}.exe
;{garbage characters}
icon=shell32.dll,7
;{garbage characters}
shell\open\command=RECYCLER\{random characters}.exe
;{garbage characters}
action=Open folder to view files
;{garbage characters}
shell\explore\command=RECYCLER\{random}}.exe
;{garbage characters}
useautoplay=1

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • {Removable Drive}:\RECYCLER

Step 7

Search and delete the file detected as WORM_DORKBOT.DCL

[ Learn More ]

Step 8

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