Malware Analysis Report (AR19-129A)
MAR-10135536-21 – North Korean Tunneling Tool: ELECTRICFISH
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This Malware Analysis Report (MAR) is the result of analytic efforts between DHS and the Federal Bureau of Investigation (FBI). Working with U.S. Government partners, DHS and FBI identified a malware variant used by the North Korean government. This malware has been identified as ELECTRICFISH. The U.S. Government refers to malicious cyber activity by the North Korean government as HIDDEN COBRA. For more information on HIDDEN COBRA activity, visit https://www.us-cert.gov/hiddencobra.
For a downloadable copy of IOCs, see:
Submitted Files (1)
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This file is a malicious Windows 32-bit executable. The application is a command-line utility and its primary purpose is to tunnel traffic between two IP addresses. The application accepts command-line arguments allowing it to be configured with a destination IP address and port, a source IP address and port, a proxy IP address and port, and a user name and password, which can be utilized to authenticate with a proxy server. It will attempt to establish TCP sessions with the source IP address and the destination IP address. If a connection is made to both the source and destination IPs, this malicious utility will implement a custom protocol, which will allow traffic to rapidly and efficiently be tunneled between two machines. If necessary, the malware can authenticate with a proxy to be able to reach the destination IP address. A configured proxy server is not required for this utility.
Figure 1 - Screenshot of the malware authenticating with the proxy server configured at command prompt.
Figure 2 - Screenshot of the malware building the authentication packet that will be sent to the destination system. It must begin with the static value "aaaa" for it to be accepted by the utility.
Figure 3 - Screenshot of the malware evaluating a received authentication packet.
Figure 4 - Screenshot of the malware system authentication packet to the source/destination system.
Figure 5 - Screenshot of the authentication packet sent to the source/destination system during analysis. The malware will attempt to tunnel traffic between the source and destination systems specified in the command prompt.