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.DHS and FBI are distributing this MAR to enable network defense and reduce exposure to North Korean government malicious cyber activity.This MAR includes malware descriptions related to HIDDEN COBRA, suggested response actions and recommended mitigation techniques. Users or administrators should flag activity associated with the malware and report the activity to the Cybersecurity and Infrastructure Security Agency (CISA) or the FBI Cyber Watch (CyWatch), and give the activity the highest priority for enhanced mitigation.This report provides analysis of one malicious 32-bit Windows executable file. The malware implements a custom protocol that allows traffic to be tunneled between a source and a destination Internet Protocol (IP) address. The malware continuously attempts to reach out to the source and the designation system, which allows either side to initiate a tunneling session. The malware can be configured with a proxy server/port and proxy username and password. This feature allows connectivity to a system sitting inside of a proxy server, which allows the actor to bypass the compromised system’s required authentication to reach outside of the network.
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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.--Begin Example Usage--Source IP/Port: 192.0.2.1:92Dest IP/Port: 198.51.100.1:92Proxy IP/Port: 203.0.113.1:92Proxy User Name: testProxy Password: testpwa12.exe -s 192.0.2.1:92 -d 198.51.100.1:92 -p 203.0.113.1:92 -u test -pw testpw--End Example Usage--After the malware authenticates with the configured proxy, it will immediately attempt to establish a session with the destination IP address, located outside of the target network and the source IP address. The header of the initial authentication packet, sent to both the source and destination systems, will be static except for two random bytes. Everything within this 34-byte header is static except for the bytes 0X2B6E, which will change during each connection attempt. Displayed below (and displayed in Figure 7) is the packet header.--Begin Authentication Packet Sent to Destination System--6161616162626262636363636464646400000000000000002B6E0000040000009210--End Authentication Packet Sent to Destination System--
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.