Mjag Downloader Trojan

Mjag is a newly observed downloader trojan built using the .NET framework and packaged using the SmartAssembly obfuscator.

Threat ID:: CC-2878
Category:: Trojan
Threat Severity:: Medium
Threat Vector:: Phishing, Email spam
Published:: 14 January 2019 12:00 AM

Report a cyber attack: call 0300 303 5222 or email [email protected]

Summary

Mjag is a newly observed downloader trojan built using the .NET framework and packaged using the SmartAssembly obfuscator.

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

Microsoft Windows - All versions

Threat details

It is delivered via malicious links distributed in small-scale spam and phishing campaigns. When opened, these links direct users to file-hosting sites, where Mjag is then downloaded to the affected device. Mjag will then copy itself to several directories before creating a registry key to maintain persistence.

Once installed, Mjag will attempt to deploy a hard-coded payload before connecting to a command and control (C2) server, however, older versions of Mjag have been observed failing to deploy their payloads correctly. This is thought to be the result of an error in the code used to contact the C2 server and is fixed in newer versions.

Remediation steps

Type	Step
	To prevent and detect a trojan 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. Regular anti-virus and security scans are performed on your organisation’s estate. 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.

Type

Step

To prevent and detect a trojan 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.
Regular anti-virus and security scans are performed on your organisation’s estate.
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: 14 February 2020 2:52 pm