Analysis by: Rhena Inocencio
ALIASES:

Ransom:Win32/Cerber (Microsoft), Win32/Filecoder.Cerber.B (ESET)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

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

It uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.

It modifies the Internet Explorer Zone Settings.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 278,528 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 04 Apr 2016
Payload: Encrypts files

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system and executes them:

  • %Application Data%\{GUID}\{random file from system32 folder}.exe - deleted after encryption routine is done

(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 component file(s):

  • %Desktop%\# DECRYPT MY FILES #.txt
  • %Desktop%\# DECRYPT MY FILES #.html
  • %Desktop%\# DECRYPT MY FILES #.vbs
  • {folders containing encrypted files}\# DECRYPT MY FILES #.txt
  • {folders containing encrypted files}\# DECRYPT MY FILES #.html
  • {folders containing encrypted files}\# DECRYPT MY FILES #.vbs
  • %Tasks%\{random filename from system32 folder}

(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.)

It uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random filename from system32 folder} = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{random filename from system32 folder} = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Command Processor
AutoRun = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

(Note:This registry entry runs the malware each time start Command Processor (Cmd.exe) is executed)

HKEY_CURRENT_USER\Control Panel\Desktop
SCRNSAVE.EXE = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
Run = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{random filename from system32 folder}.lnk - deleted after encryption routine is done

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan modifies the following file(s):

  • It renames encrypted files to {random name}.cerber

It also creates the following registry entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Printers\Defaults\
{GUID2}
Component_01 = "{base64 encoded value}"

HKEY_CURRENT_USER\Printers\Defaults\
{21BA34B1-0CCF-79AC-E63A-035913AD0523}
Component_00 = "{value}"

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan encrypts files with the following extensions:

  • .contact
  • .dbx
  • .doc
  • .docx
  • .jnt
  • .jpg
  • .mapimail
  • .msg
  • .oab
  • .ods
  • .pdf
  • .pps
  • .ppsm
  • .ppt
  • .pptm
  • .prf
  • .pst
  • .rar
  • .rtf
  • .txt
  • .wab
  • .xls
  • .xlsx
  • .xml
  • .zip
  • .1cd
  • .3ds
  • .3g2
  • .3gp
  • .7z
  • .7zip
  • .accdb
  • .aoi
  • .asf
  • .asp
  • .aspx
  • .asx
  • .avi
  • .bak
  • .cer
  • .cfg
  • .class
  • .config
  • .css
  • .csv
  • .db
  • .dds
  • .dwg
  • .dxf
  • .flf
  • .flv
  • .html
  • .idx
  • .js
  • .key
  • .kwm
  • .laccdb
  • .ldf
  • .lit
  • .m3u
  • .mbx
  • .md
  • .mdf
  • .mid
  • .mlb
  • .mov
  • .mp3
  • .mp4
  • .mpg
  • .obj
  • .odt
  • .pages
  • .php
  • .psd
  • .pwm
  • .rm
  • .safe
  • .sav
  • .save
  • .sql
  • .srt
  • .swf
  • .thm
  • .vob
  • .wav
  • .wma
  • .wmv
  • .xlsb
  • .3dm
  • .aac
  • .ai
  • .arw
  • .c
  • .cdr
  • .cls
  • .cpi
  • .cpp
  • .cs
  • .db3
  • .docm
  • .dot
  • .dotm
  • .dotx
  • .drw
  • .dxb
  • .eps
  • .fla
  • .flac
  • .fxg
  • .java
  • .m
  • .m4v
  • .max
  • .mdb
  • .pcd
  • .pct
  • .pl
  • .potm
  • .potx
  • .ppam
  • .ppsm
  • .ppsx
  • .pptm
  • .ps
  • .pspimage
  • .r3d
  • .rw2
  • .sldm
  • .sldx
  • .svg
  • .tga
  • .wps
  • .xla
  • .xlam
  • .xlm
  • .xlr
  • .xlsm
  • .xlt
  • .xltm
  • .xltx
  • .xlw
  • .act
  • .adp
  • .al
  • .bkp
  • .blend
  • .cdf
  • .cdx
  • .cgm
  • .cr2
  • .crt
  • .dac
  • .dbf
  • .dcr
  • .ddd
  • .design
  • .dtd
  • .fdb
  • .fff
  • .fpx
  • .h
  • .iif
  • .indd
  • .jpeg
  • .mos
  • .nd
  • .nsd
  • .nsf
  • .nsg
  • .nsh
  • .odc
  • .odp
  • .oil
  • .pas
  • .pat
  • .pef
  • .pfx
  • .ptx
  • .qbb
  • .qbm
  • .sas7bdat
  • .say
  • .st4
  • .st6
  • .stc
  • .sxc
  • .sxw
  • .tlg
  • .wad
  • .xlk
  • .aiff
  • .bin
  • .bmp
  • .cmt
  • .dat
  • .dit
  • .edb
  • .flvv
  • .gif
  • .groups
  • .hdd
  • .hpp
  • .log
  • .m2ts
  • .m4p
  • .mkv
  • .mpeg
  • .ndf
  • .nvram
  • .ogg
  • .ost
  • .pab
  • .pdb
  • .pif
  • .png
  • .qed
  • .qcow
  • .qcow2
  • .rvt
  • .st7
  • .stm
  • .vbox
  • .vdi
  • .vhd
  • .vhdx
  • .vmdk
  • .vmsd
  • .vmx
  • .vmxf
  • .3fr
  • .3pr
  • .ab4
  • .accde
  • .accdr
  • .accdt
  • .ach
  • .acr
  • .adb
  • .ads
  • .agdl
  • .ait
  • .apj
  • .asm
  • .awg
  • .back
  • .backup
  • .backupdb
  • .bank
  • .bay
  • .bdb
  • .bgt
  • .bik
  • .bpw
  • .cdr3
  • .cdr4
  • .cdr5
  • .cdr6
  • .cdrw
  • .ce1
  • .ce2
  • .cib
  • .craw
  • .crw
  • .csh
  • .csl
  • .db_journal
  • .dc2
  • .dcs
  • .ddoc
  • .ddrw
  • .der
  • .des
  • .dgc
  • .djvu
  • .dng
  • .drf
  • .dxg
  • .eml
  • .erbsql
  • .erf
  • .exf
  • .ffd
  • .fh
  • .fhd
  • .gray
  • .grey
  • .gry
  • .hbk
  • .ibank
  • .ibd
  • .ibz
  • .iiq
  • .incpas
  • .jpe
  • .kc2
  • .kdbx
  • .kdc
  • .kpdx
  • .lua
  • .mdc
  • .mef
  • .mfw
  • .mmw
  • .mny
  • .moneywell
  • .mrw
  • .myd
  • .ndd
  • .nef
  • .nk2
  • .nop
  • .nrw
  • .ns2
  • .ns3
  • .ns4
  • .nwb
  • .nx2
  • .nxl
  • .nyf
  • .odb
  • .odf
  • .odg
  • .odm
  • .orf
  • .otg
  • .oth
  • .otp
  • .ots
  • .ott
  • .p12
  • .p7b
  • .p7c
  • .pdd
  • .pem
  • .plus_muhd
  • .plc
  • .pot
  • .pptx
  • .psafe3
  • .py
  • .qba
  • .qbr
  • .qbw
  • .qbx
  • .qby
  • .raf
  • .rat
  • .raw
  • .rdb
  • .rwl
  • .rwz
  • .s3db
  • .sd0
  • .sda
  • .sdf
  • .sqlite
  • .sqlite3
  • .sqlitedb
  • .sr2
  • .srf
  • .srw
  • .st5
  • .st8
  • .std
  • .sti
  • .stw
  • .stx
  • .sxd
  • .sxg
  • .sxi
  • .sxm
  • .tex
  • .wallet
  • .wb2
  • .wpd
  • .x11
  • .x3f
  • .xis
  • .ycbcra
  • .yuv

It deletes the initially executed copy of itself

NOTES:

It skips to encrypt the following files or paths:

  • bootsect.bak
  • iconcache.db
  • thumbs.db
  • wallet.dat
  • \$recycle.bin\
  • \$windows.~bt\
  • \boot\
  • \drivers\
  • \program files\
  • \program files (x86)\
  • \programdata\
  • \users\all users\
  • \windows\
  • \appdata\local\
  • \appdata\locallow\
  • \appdata\roaming\
  • \public\music\sample music\
  • \public\pictures\sample pictures\
  • \public\videos\sample videos\
  • \tor browser\

It queries the affected system's country by accessing the following URL:

  • http://ipinfo.io/json
  • http://freegeoip.net/json

It executes the dropped VBS component which is responsible for speaking the following message:

Attention! Attention! Attention!
Your documents, photos, databases and other important files have been
encrypted!

It deletes all shadow copies by executing the following command:

  • vssadmin.exe delete shadows /all /quiet/

It disables Windows Startup Repair by executing the following command:

  • bcdedit.exe /set {default} recoveryenabled no bcdedit.exe /set {default} bootstatuspolicy ignoreallfailures

It opens the dropped ransom notes:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.446.08
FIRST VSAPI PATTERN DATE: 04 Apr 2016
VSAPI OPR PATTERN File: 12.447.00
VSAPI OPR PATTERN Date: 05 Apr 2016

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

Scan your computer with your Trend Micro product and note files detected as RANSOM_CERBER.CBQ1644

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

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 filename from system32 folder} = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {random filename from system32 folder} = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Command Processor
    • AutoRun = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • SCRNSAVE.EXE = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • Run = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"
  • In HKEY_CURRENT_USER\Printers\Defaults\{GUID2}
    • Component_01 = "{base64 encoded value}"
  • In HKEY_CURRENT_USER\Printers\Defaults\{21BA34B1-0CCF-79AC-E63A-035913AD0523}
    • Component_00 = "{value}"

Step 6

Deleting Scheduled Tasks

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each task that has the following value in the Schedule column:
    • {the noted malware path and filename}
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the following string:
    Cmd /c /rd /s /q C:
  5. If the said string is found, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each task that has the value in the Triggers column:
    • {the noted malware path and filename}
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the following string:
    Cmd /c /rd /s /q C:
  5. If the said string is found, delete the task..

Step 7

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.
  • %Desktop%\# DECRYPT MY FILES #.txt
  • %Desktop%\# DECRYPT MY FILES #.html
  • %Desktop%\# DECRYPT MY FILES #.vbs
  • {folders containing encrypted files}\# DECRYPT MY FILES #.txt
  • {folders containing encrypted files}\# DECRYPT MY FILES #.html
  • {folders containing encrypted files}\# DECRYPT MY FILES #.vbs
  • %User Startup%\{random filename from system32 folder}.lnk

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CERBER.CBQ1644. 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 9

Restore encrypted files from backup.


Did this description help? Tell us how we did.