RANSOM_CRYPWALL.YUYAGE
Ransom:Win32/Crowti.A (Microsoft), Trojan.Win32.Yakes.nurn (Kaspersky)
Windows
Threat Type: Trojan
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
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 does not have any propagation routine.
It does not have any backdoor routine.
It modifies the Internet Explorer Zone Settings.
It connects to certain websites to send and receive information. It deletes the initially executed copy of itself.
TECHNICAL DETAILS
270,336 bytes
EXE
Yes
16 Dec 2015
Encrypts files, Compromises system security
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:
- %Application Data%\{random characters}\{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.)
It drops the following files:
- %User Startup%\HELP_YOUR_FILES.HTML
- %User Startup%\HELP_YOUR_FILES.PNG
- %User Startup%\HELP_YOUR_FILES.TXT
- {Folder with encrypted files}\HELP_YOUR_FILES.PNG
(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.)
It drops and executes the following files:
- %Desktop%\HELP_YOUR_FILES.HTML
- %Desktop%\HELP_YOUR_FILES.PNG
- %Desktop%\HELP_YOUR_FILES.TXT
(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 adds the following processes:
- explorer.exe
- svchost.exe
It is injected into the following processes running in memory:
- created explorer.exe
- created svchost.exe
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 characters} = "%Application Data%\{random characters}\{random characters}.exe"
Other System Modifications
This Trojan modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SystemRestore
DisableSR = "1"
(Note: The default value data of the said registry entry is 0.)
Propagation
This Trojan does not have any propagation routine.
Backdoor Routine
This Trojan does not have any backdoor routine.
Web Browser Home Page and Search Page Modification
This Trojan modifies the Internet Explorer Zone Settings.
Other Details
This Trojan connects to the following website to send and receive information:
- {BLOCKED}template.com/ZjXSsD.php?{random letter}={random values}
- {BLOCKED}ia-consulting.org/8rm6Sc.php?{random letter}={random values}
- {BLOCKED}hillplaycentres.com/Kuy6q8.php?{random letter}={random values}
- {BLOCKED}gaz.pl/SCd9hX.php?{random letter}={random values}
- {BLOCKED}rvizigomme.it/vJHmkL.php?{random letter}={random values}
- {BLOCKED}e.pl/dJE2Ok.php?{random letter}={random values}
- {BLOCKED}g.tsaplin.com/8cxZ_C.php?{random letter}={random values}
- {BLOCKED}lilahiler.com/jwtfq9.php?{random letter}={random values}
- {BLOCKED}dent.ro/KqSF6e.php?{random letter}={random values}
- {BLOCKED}isi.com/2XuliT.php?{random letter}={random values}
- {BLOCKED}m.com/aVBfpT.php?{random letter}={random values}
- {BLOCKED}gpareresidence.com/ty7L18.php?{random letter}={random values}
- {BLOCKED}ept.ro/sbZFrt.php?{random letter}={random values}
It encrypts files with the following extensions:
- wll
- wmv
- wpd
- wps
- x11
- x3f
- xis
- xla
- xlam
- xlb
- xlc
- xlk
- xll
- xlm
- xlr
- xls
- xlsx
- xlsm
- xlsb
- xlt
- xltx
- xltm
- xlw
- xpp
- xsn
- ycbcra
- yuv
- zip
- 3fr
- 3dm
- 3ds
- 3gp
- 3g2
- 3pr
- 7z
- +MuhD
- ab4
- accdb
- accde
- accdp
- accdr
- accdt
- accdu
- ach
- acr
- act
- adb
- ads
- agdl
- ait
- ai
- al
- apj
- arw
- asf
- asm
- asp
- asx
- avi
- awg
- back
- backup
- backupdb
- bak
- bank
- bay
- bdb
- bgt
- bik
- bkf
- bkp
- blend
- bpw
- cdb
- cdf
- cdr
- cdr6
- cdrw
- cdr5
- cdr3
- cdr4
- cdx
- ce1
- ce2
- cer
- cfp
- cgm
- c
- cib
- class
- cls
- cmt
- cnv
- cpi
- cpp
- cr2
- craw
- crt
- crw
- csh
- csl
- csv
- cs
- dac
- db-journal
- db3
- db
- dbf
- dbr
- dbs
- dc2
- dcr
- dcs
- dcx
- ddd
- ddoc
- ddrw
- dds
- der
- des
- design
- dgc
- djvu
- dng
- doc
- docm
- docx
- dot
- dotm
- dotx
- drf
- drw
- dtd
- dwg
- dxb
- dxf
- dxg
- ebd
- edb
- eml
- eps
- erbsql
- erf
- exf
- fdb
- ffd
- fff
- fhd
- fh
- fla
- flac
- flv
- fm
- fp7
- fpx
- fxg
- gdb
- gray
- grey
- grw
- gry
- hbk
- hpp
- h
- ibank
- ibd
- ib
- ibz
- idx
- iif
- iiq
- incpas
- indd
- itdb
- java
- jpe
- jpeg
- jpg
- kc2
- kdbx
- kdc
- key
- kpdx
- lua
- m4v
- maf
- mam
- maq
- mar
- maw
- max
- mdb
- mdc
- mde
- mdf
- mdt
- mef
- mfw
- mmw
- moneywell
- m
- mos
- mov
- mp3
- mp4
- mpg
- mpp
- mrw
- mso
- myd
- ndd
- nd
- nef
- nk2
- nop
- nrw
- ns2
- ns3
- ns4
- nsd
- nsf
- nsg
- nsh
- nwb
- nx1
- nx2
- nxl
- nyf
- obj
- odb
- odc
- odf
- odg
- odm
- odp
- ods
- odt
- oil
- one
- orf
- otg
- oth
- otp
- ots
- ott
- p12
- p7b
- p7c
- pages
- pas
- pat
- pbo
- pcd
- pct
- pdb
- pdd
- pef
- pem
- pfx
- php
- pip
- plc
- pl
- pot
- potm
- potx
- ppam
- pps
- ppsx
- ppsm
- ppt
- pptm
- pptx
- prf
- ps
- psafe3
- psd
- pspimage
- ptx
- pub
- puz
- py
- qba
- qbb
- qbm
- qbr
- qbw
- qbx
- qby
- r3d
- raf
- rar
- rat
- raw
- rdb
- rm
- rpmsg
- rtf
- rw2
- rwl
- rwz
- s3db
- sas7bdat
- say
- sd0
- sda
- sdf
- sl2
- sldm
- sldx
- snp
- sqlite3
- sql
- sqlite
- sqlitedb
- sr2
- srf
- srt
- srw
- st4
- st5
- st6
- st7
- st8
- std
- sti
- stw
- stx
- svg
- swf
- sxc
- sxd
- sxg
- sxi
- sxm
- sxw
- tex
- tga
- thm
- tlg
- txt
- vob
- vsx
- vtx
- wallet
- wav
- wb2
It deletes the initially executed copy of itself
NOTES:
It searches all drives for files to encrypt except CD_ROM drive.
It deletes shadow copies by executing the following command:
- vssadmin.exe Delete Shadows/All/Quiet
It avoids encrypting files with the following extensions:
- application
- bat
- cmd
- com
- cpl
- dll
- exe
- gadget
- hta
- msc
- msi
- msp
- pif
- scf
- scr
- sys
It avoids encrypting files with the following file names:
- p0r4dime.1!
- thumbs.db
It avoids encrypting files within the following folder names:
- Temp
- Y@Cs
- cache
- cache2
- games
- nvidia
- packages
- uvOyR
- windows
It renames encrypted files using the following name:
- {5 to 10 alphanumeric characters}.{2 to 5 alphanumeric characters}
It displays the following ransom notes:
Once the victim accesses the payment site specified in the ransom note, the browser displays the following Decrypt Service site:
SOLUTION
9.800
12.214.04
16 Dec 2015
12.215.00
17 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
Step 4
Delete this registry value
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 characters} = "%Application Data%\{random characters}\{random characters}.exe"
- {random characters} = "%Application Data%\{random characters}\{random characters}.exe"
Step 5
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
- From: DisableSR = "1"
To: DisableSR = 0
- From: DisableSR = "1"
Step 6
Search and delete this file
- HELP_YOUR_FILES.HTML
- HELP_YOUR_FILES.PNG
- HELP_YOUR_FILES.TXT
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPWALL.YUYAGE. 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
Reset Internet security settings
Step 9
Scan your computer with your Trend Micro product to delete files detected as RANSOM_CRYPWALL.YUYAGE. 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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