RANSOM_CRYPWALL.YUYAIA

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 connects to a website to send and receive information. It does not have any backdoor routine.

It modifies the Internet Explorer Zone Settings.

It deletes the initially executed copy of itself.

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%\INSTRUCTIONS_{RANDOM HEX}.html
• %User Startup%\INSTRUCTIONS_{RANDOM HEX}.png
• %User Startup%\INSTRUCTIONS_{RANDOM HEX}.txt
• {Drive Letter}:\INSTRUCTIONS_{RANDOM HEX}.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%\INSTRUCTIONS_{RANDOM HEX}.html
• %Desktop%\INSTRUCTIONS_{RANDOM HEX}.png
• %Desktop%\INSTRUCTIONS_{RANDOM HEX}.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:

• svchost.exe

It is injected into the following processes running in memory:

• 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"

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan connects to the following websites to send and receive information:

• http://abcdesignbv.nl/vb4UWH.php?{random letter}={random values}
• http://arthuretpaul.com/CiY8cG.php?{random letter}={random values}
• http://arthuretpaul.com/cgi-sys/suspendedpage.cgi?{random letter}={random values}
• http://{BLOCKED}tv.altervista.org/M2auqS.php?{random letter}={random values}
• http://{BLOCKED}ndefterli.com/IAk2Qi.php?{random letter}={random values}
• http://{BLOCKED}alandais.co.nz/3fHZPS.php?{random letter}={random values}
• http://{BLOCKED}hemes.com/vwnRJG.php?{random letter}={random values}
• http://{BLOCKED}deling.ca/rHCcSm.php?{random letter}={random values}
• http://{BLOCKED}chule-gaumenfreude.de/09oq1Q.php?{random letter}={random values}
• http://{BLOCKED}h.com/oLCebS.php?{random letter}={random values}
• http://{BLOCKED}mayard.altervista.org/Dcj485.php?{random letter}={random values}
• http://{BLOCKED}pitalgroup.com/HTDyaz.php?{random letter}={random values}
• http://{BLOCKED}ablethoughts.com/QzGq85.php?{random letter}={random values}
• http://{BLOCKED}hchang.com/9vAMq_.php?{random letter}={random values}
• http://{BLOCKED}g.de/qmnKy8.php?{random letter}={random values}
• http://{BLOCKED}deocio.com/agIYZE.php?{random letter}={random values}
• http://{BLOCKED}yingboars.com/5dKXSR.php?{random letter}={random values}
• http://{BLOCKED}sparentsblog.com/Qemfzh.php?{random letter}={random values}
• http://{BLOCKED}sparentsblog.com/cgi-sys/suspendedpage.cgi?{random letter}={random values}
• http://{BLOCKED}t.sk/174DQV.php?{random letter}={random values}
• http://{BLOCKED}t.sk/YAyiWn.php?{random letter}={random values}
• http://{BLOCKED}buzz.altervista.org/oaHLO8.php?{random letter}={random values}
• http://{BLOCKED}attila.com/4t8H6r.php?{random letter}={random values}
• http://{BLOCKED}ortes.es/P35YLA.php?{random letter}={random values}
• http://www.{BLOCKED}defterli.com/IAk2Qi.php?{random letter}={random values}
• http://www.{BLOCKED}attila.com/4t8H6r.php?{random letter}={random values}
• http://{BLOCKED}tographie.free.fr/SCNnAd.php?{random letter}={random values}

It 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 encrypts files with the following extensions:

• pdf
• pot
• xlt
• pps
• xlw
• dot
• rtf
• ppt
• xls
• doc
• xml
• htm
• html
• hta
• zip
• dvr-ms
• wvx
• wmx
• wmv
• wm
• mpv2
• mpg
• mpeg
• mpe
• mpa
• mp2v
• mp2
• m1v
• IVF
• asx
• asf
• wax
• snd
• rmi
• m3u
• au
• aiff
• aifc
• aif
• midi
• mid
• wma
• wav
• m p3
• wmf
• tiff
• tif
• rle
• png
• jpeg
• jpe
• jpg
• jfif
• ico
• gif
• emf
• dib
• bmp

It renames encrypted files using the following names:

• {5 to 10 alphanumeric characters}.{2 to 5 alphanumeric characters}

It deletes the initially executed copy of itself

NOTES:

It searches all drives for files to encrypt except CD_ROM drive.

It avoids encrypting files with the following extensions:

• vb
• scr
• reg
• pif
• msi 
• exe
• com
• cmd
• bat 
• bas

It displays the following ransom notes:

Once the victim access the payment site specified in the ransom note, the browser will be display the following Decrypt Service site: