Threat Signal Report

DeadRinger: Prolonged Cyber Espionage Campaign on ASEAN Telecommunications Industry

description-logo Description

FortiGuard Labs is aware of a recent report that the telecommunications industry in the Southeast Asian region was the target of a prolonged cyber attack campaign that started back in at least 2018. Security vendor Cybereason attributed the attack campaign to several Chinese hacking groups who used Microsoft Exchange Server vulnerabilities to gain access to the victims' network. While multiple attackers were involved in the campaign, their common goal was/is persistent information theft by maintaining access to the victims' environment.

When was the Issue Reported?

Security vendor Cybereason published a report on August 3rd, 2021.

Who were the Targets of the Attack?

The targets were unnamed telecommunication companies in Southeast Asia.

What Vulnerabilities were Exploited by the Attackers?

Cybereason stated that unspecified Microsoft Exchange Server vulnerabilities were exploited in the attack. Some of the vulnerabilities were reportedly unpatched at the time of the attack.

The report indicated some of the Microsoft Exchange Server vulnerabilities exploited in the attack campaign were addressed by Microsoft in March as such those exploited vulnerabilities can be all or one of CVE-2021-26855, CVE-2021-26857, CVE-2021-26858 and CVE-2021-27065.

What was the Purpose of the Attack?

Persistent cyber espionage.

Are there any Reports of Nation State Activity Associated with the Attack?

Unconfirmed. Although the report indicates the involved hacking groups appear to have acted on on behalf of Chinese state interests, there is no concrete evidence to suggest Nation State involvement.

What Malware were Used in the Attack Campaign?

There are multiple malwares used in the attack campaign:

  • PcShare - Open source Remote Access Trojan (RAT)
  • Cobalt Strike - Legitimate tool suite that is abused the attacker
  • Mimikatz - Open source Credential-dumping tool
  • China Chopper - Web shell for creating backdoors
  • Nebulae - Backdoor
  • EnrollLogger - Keylogger

Some of the involved hacking groups also utilized "living off the land" tactics in which the attackers use whatever tools were already installed on the compromised system in the attack. This helps to hide their activity from detection.

What is the Status of Coverage?

FortiGuard Labs provides the following AV coverage against this attack campaign:








FortiGuard Labs provides the following IPS coverage against a series of Microsoft Exchange Server vulnerabilities patched by Microsoft in March, 2021:





All known network IOC's are blocked by the FortiGuard WebFiltering Client.


Traffic Light Protocol

Color When Should it Be used? How may it be shared?


Not for disclosure, restricted to participants only.
Sources may use TLP:RED when information cannot be effectively acted upon by additional parties, and could lead to impacts on a party's privacy, reputation, or operations if misused. Recipients may not share TLP:RED information with any parties outside of the specific exchange, meeting, or conversation in which it was originally disclosed. In the context of a meeting, for example, TLP:RED information is limited to those present at the meeting. In most circumstances, TLP:RED should be exchanged verbally or in person.


Limited disclosure, restricted to participants’ organizations.
Sources may use TLP:AMBER when information requires support to be effectively acted upon, yet carries risks to privacy, reputation, or operations if shared outside of the organizations involved. Recipients may only share TLP:AMBER information with members of their own organization, and with clients or customers who need to know the information to protect themselves or prevent further harm. Sources are at liberty to specify additional intended limits of the sharing: these must be adhered to.


Limited disclosure, restricted to the community.
Sources may use TLP:GREEN when information is useful for the awareness of all participating organizations as well as with peers within the broader community or sector. Recipients may share TLP:GREEN information with peers and partner organizations within their sector or community, but not via publicly accessible channels. Information in this category can be circulated widely within a particular community. TLP:GREEN information may not be released outside of the community.


Disclosure is not limited.
Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction.