RANSOM_CRYPTESLA.CBQ1635
Ransom:Win32/Tescrypt!rfn (Microsoft); Win32/Filecoder.TeslaCrypt.I trojan (ESET); Trojan horse FileCryptor.IAA (AVG);
Windows
Threat Type: Trojan
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
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 modifies the Internet Explorer Zone Settings.
It connects to certain websites to send and receive information. It gathers information and reports it to its servers.
TECHNICAL DETAILS
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:
- %Windows%\{random filename}.exe
(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
It drops the following component file(s):
- {folders containing encrypted files}\_ReCoVeRy_+{random}.png - ransom note
- {folders containing encrypted files}\_ReCoVeRy_+{random}.html - ransom note
- {folders containing encrypted files}\_ReCoVeRy_+{random}.txt - ransom note
- %My Documents%\_ReCoVeRy_+{random}.html - ransom note
- %My Documents%\_ReCoVeRy_+{random}.txt - ransom note
- %My Documents%\recover_file_{random}.txt - ransom note
(Note: %My Documents% is usually C:\Documents and Settings\{user name}\My Documents on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\Documents on Windows Vista and 7.)
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} = "C:\Windows\system32\CMD.EXE /c start %Windows%\{random filename}.exe"
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software\zzzsys
HKEY_CURRENT_USER\Software\{ID}
It adds the following registry entries:
HKEY_CURRENT_USER\Software\zzzsys
ID = "{ID}"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLinkedConnections = "1"
It modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyServer = "http=127.0.0.1:8888;https=127.0.0.1:8888;"
(Note: The default value data of the said registry entry is {user-defined}.)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyOverride = "<-loopback>"
(Note: The default value data of the said registry entry is {user-defined}.)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyEnable = "1"
(Note: The default value data of the said registry entry is {user-defined}.)
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:
- http://{BLOCKED}tecnicos.com/media/editors/wstr.php
- http://{BLOCKED}ctivo.com/wstr.php
- http://{BLOCKED}rnal.com/pmtsys/fonts/wstr.php
- http://{BLOCKED}yeli.com/wstr.php
- http://{BLOCKED}online.com/wstr.php
- http://{BLOCKED}turemediablog.com/wp-includes/fonts/wstr.php
It encrypts files with the following extensions:
- .7z
- .accdb
- .apk
- .arch00
- .asset
- .avi
- .bak
- .bar
- .bc6
- .bc7
- .big
- .bik
- .bkf
- .bkp
- .blob
- .bsa
- .cas
- .cfr
- .css
- .csv
- .d3dbsp
- .das
- .dazip
- .db0
- .dba
- .desc
- .dmp
- .docm
- .dwg
- .dxg
- .epk
- .erf
- .esm
- .ff
- .flv
- .forge
- .fos
- .fpk
- .fsh
- .gdb
- .gho
- .hkdb
- .hkx
- .hplg
- .hvpl
- .ibank
- .icxs
- .itdb
- .itl
- .itm
- .itm
- .iwd
- .iwi
- .jpeg
- .js
- .kdb
- .kf
- .layout
- .lbf
- .litemod
- .litesql
- .lrf
- .ltx
- .lvl
- .m2
- .m3u
- .m4a
- .map
- .mcmeta
- .mdb
- .mdbackup
- .mddata
- .menu
- .mlx
- .mov
- .mp4
- .mpqge
- .ncf
- .ntl
- .p12
- .p7b
- .p7c
- .pak
- .pfx
- .pkpass
- .png
- .ppt
- .pptm
- .pptx
- .psk
- .pst
- .py
- .qdf
- .qic
- .raf
- .rar
- .rb
- .re4
- .rgss3a
- .rim
- .rofl
- .rtf
- .sav
- .sb
- .sb
- .sid
- .sidd
- .sidn
- .sie
- .sis
- .slm
- .snx
- .sql
- .sum
- .svg
- .syncdb
- .t12
- .t13
- .tax
- .tiff
- .tor
- .txt
- .upk
- .vcf
- .vdf
- .vfs0
- .vpk
- .vpp_pc
- .vtf
- .w3x
- .wb2
- .wma
- .wmo
- .wmo
- .wmv
- .wpd
- .wps
- .xf
- .xlk
- .xls
- .xlsb
- .xlsm
- .xlsx
- .xxx
- .zip
- .ztmp
It gathers the following information and reports it to its servers:
- Total size of encrypted files
- OS information
- Installation ID
NOTES:
This malware encrypts files in all fixed, removable, and network drives and shares.
It deletes shadow copies by executing the following command:
WMIC.exe shadowcopy delete /nointeractive
It terminates processes containing the following strings:
- askmg
- cmd
- egedi
- rocex
- sconfi
It appends the extension .mp3 to the file name of the encrypted files. It avoids encrypting files found in the following folders:
- Windows
- Program Files
- %All Users Profile%\Application Data - if infected system is running Windows XP or older versions
- ProgramData - if infected system is running Windows Vista or newer versions
It opens ransom notes after its encryption routine.
SOLUTION
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_CRYPTESLA.CBQ1635
Step 4
Restart in Safe Mode
Step 5
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} = "C:\Windows\system32\CMD.EXE /c start %Windows%\{random filename}.exe"
- {random} = "C:\Windows\system32\CMD.EXE /c start %Windows%\{random filename}.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
- EnableLinkedConnections = "1"
- EnableLinkedConnections = "1"
Step 6
Delete this registry key
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
- zzzsys
- zzzsys
- In HKEY_CURRENT_USER\Software
- {ID}
- {ID}
Step 7
Restore this modified 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\Internet Settings
- From: ProxyEnable = "1"
To: ProxyEnable = "{user-defined}"
- From: ProxyEnable = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
- From: ProxyServer = "http=127.0.0.1:8888;https=127.0.0.1:8888;"
To: ProxyServer = "{user-defined}"
- From: ProxyServer = "http=127.0.0.1:8888;https=127.0.0.1:8888;"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
- From: ProxyOverride = "<-loopback>"
To: ProxyOverride = "{user-defined}"
- From: ProxyOverride = "<-loopback>"
Step 8
Search and delete these files
- _ReCoVeRy_+{random}.png
- _ReCoVeRy_+{random}.html
- _ReCoVeRy_+{random}.txt
- recover_file_{random}.txt
Step 9
Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPTESLA.CBQ1635. 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 10
Restore encrypted files from backup.
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