TROJ_CRYPTESLA.AC
Ransom:Win32/Tescrypt.A (Microsoft)
Windows
![](/vinfo/imgFiles/legend.jpg)
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 deletes the initially executed copy of itself.
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:
- %Application Data%\svc{random letters}.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 Profile%\My Documents\Recovery_File_{random 5 letters 1}.txt
- %Desktop%\RESTORE_FILES.HTML
- %Desktop%\RESTORE_FILES.TXT
- %Desktop%\RESTORE_FILES.BMP
(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.. %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.)
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{installation ID} = "%Application Data%\svc{random letters}.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
{installation ID} = "%Application Data%\svc{random letters}.exe"
Other System Modifications
This Trojan adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnabledLinkConnections = 1
HKEY_CURRENT_USER\Software\{installation ID}
data = {encryption information}
HKEY_CURRENT_USER\Software\msys
ID = {installation ID}
Process Termination
This Trojan terminates processes or services that contain any of the following strings if found running in the affected system's memory:
- taskmgr
- procexp
- regedit
- msconfig
- cmd.exe
Web Browser Home Page and Search Page Modification
This Trojan modifies the Internet Explorer Zone Settings.
Information Theft
This Trojan gathers the following data:
- Infection status
- Encryption key
- Bitcoin address
- Total size of encrypted files
- Malware version
- OS information
- Tor2web gateway used
- Victim's IP address
- Installation/Victim ID
Other Details
This Trojan connects to the following URL(s) to get the affected system's IP address:
- ipinfo.io/ip
It connects to the following website to send and receive information:
- https://{BLOCKED}gmutfnf.tor2web.org/{path}/{encoded information}
- https://{BLOCKED}gmutfnf.onion.to/{path}/{encoded information}
- http://{BLOCKED}gmutfnf.tor2web.org/{path}/{encoded information}
- http://{BLOCKED}gmutfnf.onion.to/{path}/{encoded information}
- http://{BLOCKED}rheath.ru/{path}/{encoded information}
- http://{BLOCKED}notube.org/{path}/{encoded information}
- http://{BLOCKED}nowbooksandgifts.com/{path}/{encoded information}
- http://{BLOCKED}ppen.nl/{path}/{encoded information}
- http://{BLOCKED}erests.com/{path}/{encoded information}
- http://{BLOCKED}marketing.com/{path}/{encoded information}
It encrypts files with the following extensions:
- .accdb
- .apk
- .arch00
- .arw
- .asset
- .avi
- .bar
- .bay
- .big
- .bik
- .bkf
- .bkp
- .blob
- .bsa
- .cas
- .cdr
- .cer
- .cfr
- .crt
- .crw
- .css
- .csv
- .d3dbsp
- .das
- .dazip
- .dba
- .dbf
- .dcr
- .der
- .desc
- .dmp
- .dng
- .doc
- .docm
- .docx
- .dwg
- .dxg
- .epk
- .eps
- .erf
- .esm
- .flv
- .forge
- .fos
- .fpk
- .fsh
- .gdb
- .gho
- .hkdb
- .hkx
- .hplg
- .hvpl
- .ibank
- .icxs
- .indd
- .itdb
- .itl
- .itm
- .iwd
- .iwi
- .jpe
- .jpeg
- .jpg
- .kdb
- .kdc
- .layout
- .lbf
- .litemod
- .lrf
- .ltx
- .lvl
- .map
- .mcmeta
- .mdb
- .mdbackup
- .mddata
- .mdf
- .mef
- .menu
- .mlx
- .mov
- .mpqge
- .mrwref
- .ncf
- .nrw
- .ntl
- .odb
- .odc
- .odm
- .odp
- .ods
- .odt
- .orf
- .pak
- .pdd
- .pef
- .pem
- .pfx
- .pkpass
- .png
- .ppt
- .pptm
- .pptx
- .psd
- .psk
- .pst
- .ptx
- .qdf
- .qic
- .raf
- .rar
- .raw
- .rgss3a
- .rim
- .rofl
- .rtf
- .rwl
- .sav
- .sid
- .sidd
- .sidn
- .sie
- .sis
- .slm
- .snx
- .sql
- .srf
- .srw
- .sum
- .svg
- .syncdb
- .tax
- .tor
- .txt
- .upk
- .vcf
- .vdf
- .vfs0
- .vpk
- .vpp_pc
- .vtf
- .wma
- .wmo
- .wmv
- .wotreplay
- .wpd
- .wps
- .xlk
- .xls
- .xlsb
- .xlsm
- .xlsx
- .xxx
- .zip
- .ztmp
- wallet
It deletes the initially executed copy of itself
NOTES:
The variable {path} can be any of the following:
- wp-content/themes/r.php?
- /inst.php?
It appends the extension .aaa to the file name of the encrypted files. It drops restore_files_{random 5 letters 2}.html and restore_files_{random 5 letters 2}.txt in all folders it traverses in searching for files to encrypt.
Computers affected by this ransomware are usually shown any of the following instructions to restore encrypted files:
![](http://documents.trendmicro.com/images/TROJ_CRYPTESLA_AC_IMG1.jpg)
![](http://documents.trendmicro.com/images/TROJ_CRYPTESLA_AC_IMG2.jpg)
![](http://documents.trendmicro.com/images/TROJ_CRYPTESLA_AC_IMG3.jpg)
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
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- {installation ID} = "%Application Data%\svc{random letters}.exe"
- {installation ID} = "%Application Data%\svc{random letters}.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
- {installation ID} = "%Application Data%\svc{random letters}.exe"
- {installation ID} = "%Application Data%\svc{random letters}.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
- EnabledLinkConnections = 1
- EnabledLinkConnections = 1
Step 4
Reset Internet security settings
Step 5
Search and delete these files
- %Desktop%\RESTORE_FILES.HTML
- %Desktop%\RESTORE_FILES.TXT
- %Desktop%\RESTORE_FILES.BMP
- restore_files_{random 5 letters 2}.html
- restore_files_{random 5 letters 2}.txt
Step 6
Scan your computer with your Trend Micro product to delete files detected as TROJ_CRYPTESLA.AC. 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.
NOTES:
Restore encrypted files from backup.
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