Threat Advisory: Ransom Cryptolocker
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- Bu səhifədəki naviqasiya:
- Infection and Propagation Vectors
- Knowledge Center
- New files being created
- Files being executed
- Write access to files and New files being created
- File or folder name to block
- *** Disclaimer
- New Variant (November 2014)
- Characteristics and Symptoms Description
- List of file types the malware encrypts
- Getting Help from the McAfee Foundstone Services team
| McAfee Labs Threat Advisory
November 12, 2014 McAfee Labs periodically publishes Threat Advisories to provide customers with a detailed analysis of prevalent malware. This Threat Advisory contains behavioral information, characteristics, and symptoms that may be used to mitigate or discover this threat, and suggestions for mitigation in addition to the coverage provided by the DATs.
To receive a notification when a Threat Advisory is publ ished by McAfee Labs, select to receive “Malware and Threat Reports” at the following URL : https://sns.snssecure.mcafee.com/content/signup_login .
Ransom Cryptolocker is a ransomware that on execution locks the user's system, thereby leaving the system in an unusable state. It also encrypts the list of file types present in the user ’ s system. The compromised user has to pay the attacker with a ransom to unlock the system and to get the files decrypted.
McAfee detects this threat under the following detection name[s]:
Ransom-[Variant Name]!partialMD5
Detailed information about the threat, its propagation, characteristics, and mitigation are in the following sections:
Infection and Propagation Vectors
Mitigation
Characteristics and Symptoms
Restart Mechanism
McAfee Foundstone Services
Infection and Propagation Vectors The malware is being propagated via malicious links in spam emails, which leads to pages exploiting common system vulnerabilities. These exploit pages will drop Ransom Cryptolocker and other malicious executable files on the affected machine.
A recent variant of the malware is still using spam as a propagation vector, but instead of links to exploit sites, it comes with an attachment in the form of a Word file. The Word document contains a VB macro that will download the malware directly to the user ’ s machine. When opened, the document will attempt to disguise as a valid Microsoft Office warning telling the user to enable Macros, like in the following example:
Figure 1: Office document with Macro The spam message is targeting mainly users in the Netherlands, even though infections can occur anywhere due to the methods used in propagation. The Subjects seen so far include these:
Den Haag - Incassoburea Nederland.
Den Haag - Intrum Incasso
Den Haag Incasso Nederland.
INCASSO NEDERLAND.
*INCASSO* NEDERLAND. The attachments are .doc or .zip files that may be named as one of the following examples:
Order5611041101.doc
Order561104146.doc
Order561104112.zip
Order561104133.zip
Processing1011201435.doc
Processing1011201435.zip
The malicious documents being used in these spam campaigns are detected by the following name[s]:
W97M/Downloader.[variant name]
Coverage for the above mentioned detection names are available from the production DAT 7623. Mitigation Mitigating the threat at multiple levels such as file, registry, and URL could be achieved at various layers of McAfee products. Browse the product guidelines available here
(click Knowledge Center, and select Product Documentation from the Content Source list) to mitigate the threats based on the behavior described below in the “ Characteristics and symptoms ” section.
Refer the following KB articles to configure Access Protection rules in VirusScan Enterprise:
KB81095 -
How to create a user-defined Access Protection Rule from a VSE 8.x or ePO 5.x console
KB54812
- How to use wildcards when creating exclusions in VirusScan Enterprise 8.x
Ransom Cryptolocker usually installs itself into the Application Data folder. However, the new variant is installed in the C:\Windows folder with a random filename, like the following example:
C:\WINDOWS\ixineden.exe
It also creates a folder in %APPDATA% to save its configuration files:
C:\Documents and Settings\All Users\Application Data\oziqemegewypyvuh Users can configure and test Access Protection Rules to restrict the creation of new files and folders when there are no other legitimate uses.
Select New files being created and add the following file location in File or folder name to block:
[OS installed drive]\Documents and Settings\[logged in user]\ Application Data\*.exe [For windows XP]
[OS installed drive]\Users\[logged in user]\AppData\Roaming \*.exe [ For Windows 7]
It is also recommended that you select and test the Files being executed option for the above folders, and add only known legitimate programs under the Application Data folder to Processes to exclude.
Also, users can configure Access Protection Rules to prevent the files from being encrypted by the Cryptolocker. Select Write access to files and New files being created. Include the following file location in Processes to include:
[OS installed drive]\Documents and Settings\[logged in user]\ Application Data\*.exe [ For windows XP]
Similarly, add the file type in File or folder name to block to prevent the encryption. Users can configure similar rules for all other file types that are encrypted by Cryptolocker.
For blocking all types of files being modified by Cryptolocker, use:
[OS installed drive]\Documents and Settings\[logged in user]\ Application Data\*.* [ For windows XP]***
[OS installed drive]\Users\[logged in user]\AppData\Roaming \*.* [ For Windows 7]***
To blacklist applications using a Host Intrusion Prevention custom signature, refer to KB71329
. To create an application blocking rules policies to prevent the binary from running, refer to KB71794 .
executable, refer to KB71794
. To block attacks from a specific IP address through McAfee Nitrosecurity IPS, refer to KB74650 .
*** Disclaimer: Use of *.* in an access protection rule would prevent all types of files from running and being accessed from that specific location. If specifying a process path under Processes to Include, the use of wildcards for Folder Names may lead to unexpected behavior. Users are requested to make this rule as specific as possible.
Because the new variant uses spam attachments to spread, users may want to follow some other mitigation procedures to avoid this threat:
Instruct users to not open unknown or unsolicited attachments.
Ensure Microsoft Office Security policies for macros are set to High or Very High.
Ensure GTI is enabled on gateway devices and endpoints.
Ensure there are no allow list policies that exempt .doc/.docx attachments from spam/AV scanning.
Deny messages with the following subjects:
Den Haag - Incassoburea Nederland.
Den Haag - Intrum Justitia
Den Haag - Intrum Incasso
Den Haag Incasso Nederland.
INCASSO NEDERLAND.
*INCASSO* NEDERLAND.
Users of the following products may want to check if GTI is enabled in order to block the IP addresses being used to send spam:
SaaS
Email & Web Security 5.6
Email Gateway (7.x or later) 7.5
Email Gateway (7.x or later) 7.0
GroupShield for Microsoft Exchange 7.0.x
Desktop users need to enable the Outlook plugin and also install the Site Advisor browser plugin to detect the spam attachment before it is opened and block access to the malicious domains.
Description Ransom Cryptolocker belongs to a family of malware that encrypts the compromised user files available in the system and demands the user to pay a ransom to retrieve the files. The contents of the original files are encrypted using AES Algorithm with a randomly generated key.
Once the system is infected, the malware binary first tries to connect to a hard coded command and control server with IP address 184.164.136.134. If this attempt fails, it generates a domain name using random domain name algorithm and appends it with one among the following domain names:
.org
.net
.co.uk
.info
.com
.biz
.ru
Once the system initiates the communication with the remote C&C server, the malware binary proceeds to the next step, which is to encrypt the compromised user files in the system. After generating the AES encryption key and submitting it to the C&C server, the malware binary searches for the below mentioned file types in the user system fixed and removable devices.
*.odt *.xls
*.pst img_*.jpg *.mrf *.cer
*.ods *.xlsx
*.dwg *.dng
*.nef *.crt
*.odp *.xlsm
*.dxf *.arw
*.nrw *.pem
*.odm *.xlsb
*.dxg *.srf
*.orf *.pfx
*.odc *.xlk
*.wpd *.bay
*.raf *.eps
*.odb *.ppt
*.rtf *.crw
*.raw *.indd
*.doc *.pptx
*.mdf *.dcr
*.ptx *.cdr
*.docx *.pptm
*.dbf *.kdc
*.pef ????????.jpg *.docm *.mdb
*.psd *.erf
*.srw ????????.jpe *.wps *.accdb
*.pdd *.mef
*.der
Encryption Technique The malware uses an AES algorithm to encrypt the files. The malware first generates a 256-bit AES key and this will be used to encrypt the files. In order to be able to decrypt the files, the malware author needs to know that key. To avoid transmitting the key in clear text, the malware will encrypt it using an asymmetric key algorithm, namely the RSA public/private key pair.
This newly generated AES key is encrypted using the unique RSA public key created by the malware author and present in the malicious executable. This encrypted key is then submitted to the C&C server. The only way to recover the key after the malware finishes executing is by having the RSA private key associated with the public key used.
This key is only known to the malware author, and is never transmitted via the network or present in the infected
machine. Hence, it’s impossible to recover the user’s encrypted files without that key after they have been infected.
Once the system is compromised, the malware displays the below mentioned warning to the user and demand ransom to decrypt the files.
Figure 2: Ransom Cryptolocker Desktop wallpaper Figure 3: Ransom Cryptolocker Warning Message
Figure 4: New variant of Cryptolocker targeting Dutch users.
It maintains the list of files that were encrypted by this malware under the following registry entry:
HKEY_CURRENT_USER\Software\CryptoLocker\Files
On execution, this malware binary copies itself to %AppData% location and deletes itself using a batch file:
%AppData%\{2E376276-3A5A-0712-2BE2-FBF2CFF7ECD5}.exe
%AppData% refers to the current user’s Applica tion data location.
The malware author receives the ransom amount from the compromised user from one among the following payment methods:
Figure 4. Payment methods used by the attackers Network Connections Cryptolocker uses the DGA ( Domain Generation Algorithm ) to generate the Random Domain names hourly based.
The following are some of the observed domains of the C&C servers: soudpmiyvxmd.org wxfaxwfotkcp.co.uk avlpfgiqwdudk.info irvggrirvsqqy.com gbpboroxfiep.co.uk xvaqocjidsht.info ngmneoxxoisqk.com jnwsjavtnkvmh.net ofoauksakmgs.info soywduppiyvf.com udsmjlwhfkmeg.net dyddkwwieairg.biz crjxtpyytwxf.com tmtntatjrhbj.net intkitmowpkrw.biz euepnfkkvrnnf.ru qgyvutxttqaj.net upjsdeujrdpv.biz vlqtsbjlaojjg.ru ehbktmjmyefwg.org estttyesdbrv.biz vnejtjydblua.ru jvrrrjysrthwg.org fdcwwuwoqvkso.co.uk
uwuexnaukgiy.ru ynnivqvmcyxxr.org hjxywcvnbotlg.co.uk fxcyhrpfigvcu.info vupuoseotond.org mxoguylttevli.co.uk ifylakjpsgyhf.info sidwgwvsyqlxu.com hdauthcpbwblw.net oxibtrwnccaej.org ntmpidpuhvjxm.com pykluscfamoho.biz unbssmidrhqhn.biz dsfyhcdkeiprs.co.uk opnclitaxswlu.net qulxxxgkqjcun.ru bnhdumqalrkij.ru qdgwghjxusfnj.info igemsolqdaotb.org jjrtvxqpkhxem.org loppindadxdnv.info mkqclshftuqbu.com tnfhkwqywydsb.net hxgfjfggoebgr.biz uvdotgvjluqgb.ru
New Variant (November 2014)
As of November 2014 a new variant of Cryptolocker was found targeting users in the Netherlands. This new variant performs basically the same actions as previous ones, but with some important differences.
The threat is now using VB macros in .doc files attached to email to spread. The documents need to be opened by the user, and macros must be active for the download to occur.
Once the macro is enabled, the following domain will be contacted to download the actual Cryptolocker sample:
Hxxp : // imagecenterdown.ru / info.png
Hxxp : // officeimage.ru / a.png
Hxxp : // officeimage.ru / b.png
Hxxp : // officeimage.ru / image.png
The sample will be executed and will inject itself into Explorer before executing the malicious functions. The first action after running is to contact the following site to post the generated key and receive information about the infection:
Deadwalk32.ru
It also tries to delete any information about Shadow Copy to avoid files being recovered by the user:
vssadmin.exe Delete Shadows /All /Quiet
Another change from the previous version is that this one seems to be capable of stealing contacts from local email clients to send spam. The malware will scan the system for the following files and registry keys to collect email addresses:
eabook.mab
history.mab
Thunderbird\Profiles\
HKCU\Software\Microsoft\Internet Account Manager\Accounts\00000001
HKCU\Software\Microsoft\Office\Outlook\OMI Account Manager\Accounts
HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Microsoft Outlook Internet Settings
HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook
After that, as in previous variants, the malware will start encrypting all files with specific extensions on the machine, adding the extension .encrypted to them. Restart Mechanism The following registry entry would enable the Trojan to execute every time when Windows starts:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\ o
CryptoLocker "%AppData%\{2E376276-3A5A-0712-2BE2-FBF2CFF7ECD5}.exe"
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ o
ywupytit: "C:\WINDOWS\ufivehen.exe"
Getting Help from the McAfee Foundstone Services team This document is intended to provide a summary of current intelligence and best practices to ensure the highest level of protection from your McAfee security solution. The McAfee Foundstone Services team offers a full range of strategic and technical consulting services that can further help to ensure you identify security risk and build effective solutions to remediate security vulnerabilities. You can reach them here: https://secure.mcafee.com/apps/services/services-contact.aspx
This Advisory is for the education and convenience of McAfee customers. We try to ensure the accuracy, relevance, and timeliness of the information and events described; they are subject to change without notice.
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