Trend Micro has observed recently that threat actors have been sending massive spam emails distributing Locky Ransomware. The cybercriminals behind this email campaign appear to be using social engineering tactics to entice users into opening a file attachment, which in turn downloads the Locky ransomware and encrypts users’ data.
Encrypted Data Files by the recent Locky Ransomware Campaign
ARRIVAL AND INSTALLATION
The infection chain of this ransomware campaign starts with a socially-engineered email. Threat actors send social engineered email bundled with a spoofed “Herbalife” brand, an email that impersonates a “copier” file delivery or an email with subject line of “Emailing - (name of attachment)”. All of the affected emails contain an archive (7zip, rar, zip) which has an embedded VBscript file. When executed, the script connects to command and control (C&C) servers to download the Locky Ransomware, which then encrypts the users’ data locally as well as the files on network shares. It has also been observed recently that “Fake voicemail email notifications” are being used by this ransomware campaign as well.
Locky Email Campaign Infection Chain
Sample spam mails used by Locky ransomware campaign:
Spoofed Herbal Life Brand Email
Email that impersonates a “copier” file delivery
Email with subject line “Emailing - (name of attachment)”.
Messaging products such as Trend Micro InterScan Messaging Security Virtual Appliance (IMSVA) and ScanMail for Exchange (SMEX) can block spam mails related to this ransomware. They check for email reputation and web reputation of the embedded links, file attachments, as well as macros in MS Office documents.
Instructions on how to enable Ransomware Protection Feature for IMSS and IMSVA:
Web Reputation Services evaluates the potential security risk of all requested URLs at the time of each HTTP request. Depending on the rating returned by the database and the security level configured, web reputation either blocks or approves the request.
Web Reputation service already blocks all of the known URLs associated with Locky ransomware campaign.
Trend Micro Deep Discovery Inspector (DDI) is helpful in identifying the potentially impacted machines on the network because it has the following detection rules for this ransomware:
- Rule ID 3601: VBSCRDLX – HTTP (Request) - ETA: September 26, 2017
- Rule ID: 2116 LOCKY - Ransomware - HTTP (Request) - Variant 2
- Rule ID: 2028 LOCKY - Ransomware - HTTP (Request)
- Rule ID: 2251 LOCKY - Ransomware - HTTP (Request) - Variant
- Rule ID 2409: File renamed - LOCKY- Ransomware - SMB (Request) - ETA: September 26, 2017
Deep Security has an IPS solution that can help detect and block Locky Ransomware-associated network traffic.
Instructions on how to enable this feature can be viewed from this link: Ransomware Detection and Prevention in Deep Security.
TippingPoint has the following ThreatDV to block and prevent threat activity related to Locky Ransomware:
- 26222: HTTP: Locky CnC checkin Nov 21
- 26223: HTTP: Locky CnC checkin Nov 21 M2
- 26226: HTTP: Locky CnC Checkin Dec 5 M1
- 26227: HTTP: Locky CnC Checkin HTTP Pattern
- 27857: HTTP: Locky CnC checkin Aug 03
BEST PRACTICES FOR IT ADMINS
- Optimize email security. Blocking malicious emails at the gateway level before they can even reach the users will help prevent malware infections.
- Review the need for VBS and JS scripting in the machine. If it is not needed, you can disable it to reduce the risk of malware infection.
- Officecan Behavior Monitoring can block wscript/cscript on the machine: Blocking .vbs malware by disabling the Windows Script Host (WSH) in OfficeScan (OSCE)
- Microsoft also provides a guide on how to disable wscript in the computer: Disabling Windows Script Host
- Don’t enable macros in MS Office file attachments received via email.
- Restrict write permissions on the file server if possible. Ransomware encrypts files for both local and network shares with write permissions.
- Back up important files regularly. Cybercriminals use the potential loss of important and personal data as a fear-mongering tactic to coerce victims into paying the ransom. Organizations and end users can back up files to remove their leverage. Keep at least three copies, with two stored in different devices, and another in an offsite or safe location.
- Effective Patch Management. It is highly recommended to keep application patch levels up-to-date as a lot of malware use these vulnerabilities to compromise your machine. Examples of critical applications are Java, Adobe, and your Internet Browser.
- Educate users about social engineering attacks. Getting infected by Ransomware is an indication that the user is not security aware. The user may receive spam mail and open the attachment without knowing the risks involved.