Analysis by: RonJay Kristoffer Caragay
ALIASES:

Backdoor.IRCBot (Malwarebytes); Trojan.MSIL.IRCBot (Ikarus); Riskware/Flooder (Fortinet); Trojan:Win32/Skeeyah.A!rfn (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

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 does not have any propagation routine.

It connects to Internet Relay Chat (IRC) servers. It joins an Internet Relay Chat (IRC) channel. It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 26,624 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 23 Jun 2015
Payload: Connects to URLs/IPs

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 the following copies of itself into the affected system:

  • %Application Data%\LolClient\Local Store\cache940.exe

(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.)

It drops the following files:

  • %User Temp%\{random filename 1}.tmp ← deleted afterwards
  • %User Temp%\{random filename 1}.0.cs ← source file script; deleted afterwards
  • %User Temp%\{random filename 1}.cmdline ← command line script; deleted afterwards
  • %User Temp%\{random filename 1}.out ← deleted afterwards
  • %User Temp%\{random filename 1}.err ← deleted afterwards
  • %User Temp%\{random 1}.tmp ← config file; deleted afterwards
  • %User Temp%\{random 2}.tmp ← config file; deleted afterwards

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

It drops and executes the following files:

  • %User Temp%\{random}.exe ← watchdog component

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

It creates the following folders:

  • %Application Data%\LolClient\Local Store

(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.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • dgsdfgey435y5styhhaeth → main process
  • dgsdfgey435y5styhhaethppp → watchdog component

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
LolCache940 = "%Application Data%\LolClient\Local Store\cache940.exe"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
StartupApproved\Run
LolCache940 = "02 00 00 00 00 00 00 00 00 00 00 00"

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

  • TCP 6667

It connects to any of the following Internet Relay Chat (IRC) servers:

  • {BLOCKED}.{BLOCKED}.147.109

It joins any of the following Internet Relay Chat (IRC) channels:

  • #faggot

It executes the following commands from a remote malicious user:

  • auth → add sender
  • jsbypass → Get and Clear Cookies
  • http → Performs HTTP Flood
  • condis → Performs rapid Connect\Disconnect Flood
  • tcp → Performs TCP Flood
  • udp → Performs UDPFlood
  • stopdos → Stop All DDOS attack
  • dlexec → Download and execute file
  • update1 → Update itself
  • uninstall → Remove Auto-Run Registry and copy of itself
  • exit → Terminate itself

It accesses a remote Internet Relay Chat (IRC) server where it receives the following commands from a remote malicious user:

  • USER
  • NICK
  • PING
  • PONG
  • JOIN
  • PRIVMSG
  • MODE

Download Routine

This backdoor saves the files it downloads using the following names:

  • %Application Data%\LolClient\Local Store\{random characters}.exe

(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:

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.750

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • LolCache940 = "%Application Data%\LolClient\Local Store\cache940.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run
    • LolCache940 = "02 00 00 00 00 00 00 00 00 00 00 00"

Step 5

Search and delete these folders

[ 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.  
  • %Application Data%\LolClient\Local Store\

Step 6

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.
  • %User Temp%\{random}.exe

Step 7

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

Step 8

Scan your computer with your Trend Micro product to delete files detected as BKDR_IRCBOT.ER. 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.


Did this description help? Tell us how we did.