Pierluigi Paganini May 30, 2018

The Department of Homeland Security (DHS) and the FBI issued a joint Technical alert on two strain on malware, the Joanap backdoor Trojan and Brambul Server Message Block worm, associated with the HIDDEN COBRA North Korea-linked APT group.

The US-CERT alert reads:

“Working with U.S. government partners, DHS and FBI identified Internet Protocol (IP) addresses and other indicators of compromise (IOCs) associated with two families of malware used by the North Korean government:

• a remote access tool (RAT), commonly known as Joanap; and
• a Server Message Block (SMB) worm, commonly known as Brambul.” 

“The U.S. Government refers to malicious cyber activity by the North Korean government as HIDDEN COBRA.”

The government experts have identified a range of IP addresses and other indicators of compromise (IOCs) associated with the two families of malware.

The first threat tracked as “Joanap” is a two-stage RAT that uses peer-to-peer communications to manage botnets and perform malicious activities such as data exfiltration, installation of further payloads and establish proxy communications on compromised Windows systems.

“Joanap is a two-stage malware used to establish peer-to-peer communications and to manage botnets designed to enable other operations. Joanap malware provides HIDDEN COBRA actors with the ability to exfiltrate data, drop and run secondary payloads, and initialize proxy communications on a compromised Windows device.” states the alert.

The second malware analyzed by the government researchers is a Windows 32-bit  Server Message Block (SMB) worm called “Brambul”.

Brambul is used as a service dynamic link library file or a portable executable file often dropped and installed onto target networks by dropper malware.

“When executed, the malware attempts to establish contact with victim systems and IP addresses on victims’ local subnets. If successful, the application attempts to gain unauthorized access via the SMB protocol (ports 139 and 445) by launching brute-force password attacks using a list of embedded passwords. Additionally, the malware generates random IP addresses for further attacks.” states the ransomware.

Network administrators could use the IOCs included in the alert to detect both Joanap and Brambul malware and prevent infections.

Pierluigi Paganini

(Security Affairs – HIDDEN COBRA, hacking)

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