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Win32/Troldesh

First posted on 20 April 2015.
Source: Microsoft

Aliases :

There are no other names known for Win32/Troldesh.

Explanation :

Threat behavior

Installation

The threat creates the following files:

• %APPDATA%\windows\crsrss.exe - copy of the malware
• %TEMP%\state.tmp - temporary file used for the encryption

It changes the following registry entry so that it runs each time you start your PC:

In subkey: HKLM\Software\Microsoft\Windows\CurrentVersion\Run
Sets value: "Client Server Runtime Subsystem"
With data: "%APPDATA%\windows\crsrss.exe"

Payload

Encrypts your files

This threat encrypts files on your PC that have the following extensions:

• .3ds
• .3fr
• .3g2
• .3gp
• .7z
• .accda
• .accdb
• .accdc
• .accde
• .accdt
• .accdw
• .adb
• .adp
• .ai
• .ai3
• .ai4
• .ai5
• .ai6
• .ai7
• .ai8
• .anim
• .arw
• .as
• .asa
• .asc
• .ascx
• .asm
• .asmx
• .asp
• .aspx
• .asr
• .asx
• .avi
• .avs
• .backup
• .bak
• .bay
• .bd
• .bin
• .bmp
• .bz2
• .c
• .cdr
• .cer
• .cfc
• .cfm
• .cfml
• .chm
• .cin
• .class
• .config
• .cpp

• .cr2
• .crt
• .crw
• .cs
• .css
• .csv
• .cub
• .dae
• .dat
• .dbf
• .dc3
• .dcm
• .dcr
• .der
• .dib
• .dic
• .dif
• .divx
• .djvu
• .dng
• .doc
• .docm
• .docx
• .dot
• .dotm
• .dotx
• .dpx
• .dqy
• .dsn
• .dtd
• .dwg
• .dwt
• .dx
• .dxf
• .edml
• .emf
• .emz
• .eps
• .epsf
• .epsp
• .erf
• .exr
• .f4v
• .fido
• .flm
• .flv
• .fxg
• .gif
• .gz
• .h
• .hdr
• .hpp

• .hta
• .htc
• .htm
• .html
• .icb
• .ics
• .iff
• .inc
• .indd
• .ini
• .iqy
• .j2c
• .j2k
• .java
• .jp2
• .jpc
• .jpe
• .jpeg
• .jpf
• .jpg
• .jpx
• .js
• .jsf
• .json
• .jsp
• .kdc
• .kmz
• .lasso
• .lbi
• .m1v
• .m4a
• .m4v
• .max
• .mda
• .mdb
• .mde
• .mdf
• .mdw
• .mef
• .mfw
• .mht
• .mhtml
• .mka
• .mkidx
• .mkv
• .mos
• .mov
• .mp3
• .mp4
• .mpeg
• .mpg
• .mpv

• .mrw
• .msg
• .nef
• .nrw
• .obj
• .odb
• .odc
• .odm
• .odp
• .ods
• .oft
• .one
• .onepkg
• .onetoc2
• .oqy
• .orf
• .p12
• .p7b
• .p7c
• .pam
• .pbm
• .pct
• .pcx
• .pdd
• .pdf
• .pdp
• .pef
• .pem
• .pfm
• .pfx
• .pgm
• .php
• .php3
• .php4
• .php5
• .phtml
• .pict
• .pl
• .pls
• .pm
• .png
• .pnm
• .pot
• .potm
• .potx
• .ppa
• .ppam
• .ppm
• .pps
• .ppsm
• .ppt
• .pptm

• .pptx
• .prn
• .ps
• .psb
• .psd
• .pst
• .ptx
• .pub
• .pxr
• .py
• .qt
• .r3d
• .raf
• .rar
• .raw
• .rdf
• .rgbe
• .rle
• .rqy
• .rss
• .rtf
• .rw2
• .rwl
• .sct
• .sdpx
• .shtm
• .shtml
• .slk
• .sln
• .sql
• .sr2
• .srf
• .srw
• .ssi
• .stm
• .svg
• .svgz
• .swf
• .tab
• .tar
• .tdi
• .tga
• .thmx
• .tif
• .tiff
• .tld
• .torrent
• .tpl
• .txt
• .u3d
• .udl
• .uxdc

• .vb
• .vbs
• .vcs
• .vda
• .vdr
• .vdw
• .vdx
• .vsd
• .vss
• .vst
• .vsw
• .vsx
• .vtm
• .vtml
• .vtx
• .wav
• .wb2
• .wbm
• .wbmp
• .wim
• .wmf
• .wml
• .wmv
• .wpd
• .wps
• .x3f
• .xl
• .xla
• .xlam
• .xlk
• .xlm
• .xls
• .xlsb
• .xlsm
• .xlsx
• .xlt
• .xltm
• .xltx
• .xlw
• .xml
• .xps
• .xsd
• .xsf
• .xsl
• .xslt
• .xsn
• .xtp
• .xtp2
• .xyze
• .xz
• .zip

It renames the encrypted file in the format =.xbtl, for example DWoqBAnMDpI9ij0IjGn1uaRpz-jzei37J5dFIrnROGE=.xtbl.

After it encrypts your files, the threat drops a ransom note in each folder where it encrypted files. The note has the file name in the format README.txt (for example, README8.txt) and looks like the following:



It also displays a wallpaper that looks like the following:



We've also seen the threat connect to the following remote servers on ports 443 and 80 to send information about your PC to a remote attacker:

• 131.188.40.189
• 194.109.206.212
• 208.83.223.34
• 86.59.21.38

Analysis by Marianne Mallen

Symptoms

The following can indicate that you have this threat on your PC:

• You can't open your files
• You see a message like the following:
  
  

Last update 20 April 2015

 

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