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Rozena File-less Backdoor Malware

Rozena, also known as Bedep, is a backdoor malware first observed in 2015.

Threat ID:
CC-2524
Category:
Backdoor
Threat Severity:
Medium
Threat Vector:
Email spam, Phishing, Drive by download, Download
Published:
3 July 2018 12:00 AM
Report a cyber attack: call 0300 303 5222 or email [email protected]

This content has been archived

This article no longer conforms to NHS Digital's standards for cyber alerts, and may contain outdated or inaccurate information. Use of this information contained in this page is at your own risk

Summary

Rozena, also known as Bedep, is a backdoor malware first observed in 2015.

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

  • Microsoft Windows - All versions

Threat details

It has recently reappeared using a new file-less format to reduce detection from anti-virus and security products.

Rozena is typically distributed as an executable file, disguised as a Microsoft Word document, through a number of different delivery vectors. These vectors include; malicious attachments in spam or phishing campaigns, drive-by-downloads from compromised sites and downloaded by secondary malware. Once opened, this executable creates an encrypted text file and an obfuscated PowerShell script called CREATOR. CREATOR is responsible for creating a secondary script called DECODER, which then decrypts the text file to obtain a final script referred to as INJECTOR

INJECTOR will then inject the Rozena shellcode into the targeted system and initiate communications with a command and control server using a reverse TCP connection. Once installed, Rozena provides a remote attacker with full access to the affected system; although at the time of publication it is unclear what their intention is.

Remediation advice

Additionally, to prevent and detect an infection ensure that:

  • A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails.
  • All operating systems, anti-virus and other security products are kept up-to-date.
  • All day-to-day computer activities such as email and internet are performed using non-administrative accounts.
  • Strong password policies are in place.
  • Network, proxy and firewall logs s

Remediation steps

Type Step
  • PowerShell Constrained Language Mode can be set to limit the capability of PowerShell scripts by preventing them from using .Net or Windows API calls.
  • Unauthorised binary execution can also be prevented by pairing PowerShell with AppLocker.
  • As a file-less application, Rozena can be terminated by rebooting the affected device or system.

Additionally, to prevent and detect an infection ensure that:

  • A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails.
  • All operating systems, anti-virus and other security products are kept up-to-date.
  • All day-to-day computer activities such as email and internet are performed using non-administrative accounts.
  • Strong password policies are in place.
  • Network, proxy and firewall logs should be monitored for suspicious activity.
  • User accounts accessed from affected devices should be reset on a clean computer.
  • Your organisation adopts a holistic all-round approach to Cyber Security as advocated by the 10 Steps to Cyber Security.

Last edited: 31 January 2022 9:34 am