Mysa Remote Access Trojan

First observed in early 2017, Mysa is a remote access trojan that uses the EternalBlue SMBv1 exploit to propagate.

Threat ID:: CC-2999
Category:: Trojan
Threat Severity:: Medium
Threat Vector:: Exploit, Insecure network, Email spam
Published:: 1 April 2019 12:00 AM

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

Summary

First observed in early 2017, Mysa is a remote access trojan that uses the EternalBlue SMBv1 exploit to propagate.

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

Microsoft Windows - Versions 10, 8.1, 8 and 7

Windows 10

Windows 7

Threat details

Believed to have been created in the weeks after EternalBlue was publicly disclosed by the Shadow Brokers, it appeared to have fallen out of use but has recently begun appearing in new attacks.

At the time of publication it is unclear how Mysa is initially delivered to systems, although there are unconfirmed reports indicating it may be distributed via targeted spam campaigns as an embedded Dynamic Link-Library (DLL) file.

This DLL file will connect to a command and control (C2) server when executed, before terminating specific user accounts, files and processes. It will then create two registry entries to gain persistence and download a number of files, including a second stage payload. This second stage appears to be a modified version of a Chinese remote administration tool known as ForShare. When executed, it will connect to a separate C2 server before deploying the EternalBlue exploit to propagate to other devices on the network. Once this is done it will close port 445, likely in an attempt to prevent infection from other malware using EternalBlue.

Remediation steps

Type	Step
	Users and administrators are advised to install the Microsoft critical security bulletin MS17-010 immediately if they have not already done so. 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

Users and administrators are advised to install the Microsoft critical security bulletin MS17-010 immediately if they have not already done so.

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 2:51 pm