Threat Signal Report

MESSAGETAP/APT41 Activity

Description

What is the issue specifically?

The FortiGuard Labs SE team is aware of a new state sponsored attack dubbed "MESSAGETAP" discovered by researchers at FireEye. MESSAGETAP is an infostealer that can steal SMS text messages, IMSI numbers and specific keywords for later exfiltration. This new APT is assigned the number 41, which follows the nomenclature of FireEye's naming convention. FireEye has attributed APT41 to China.


How was this discovered?

FireEye states this sample was discovered in 2019 during an investigation of an unnamed telecom provider.


What is the threat specifically?

MESSAGETAP is a 64-bit ELF file that is designed to exfiltrate information from servers hosting SMS services, IMSI data and any other specific keywords targeted by the attackers. The malware looks for the creation of two specific text files keyword_parm.txt and parm.txt on the targeted machine and will check the contents of these files every 30 seconds. Contained within these text files is logged data that contains IMSI numbers, which is a number that uniquely identifies every individual caller of a mobile network. It is stored in a 64-bit field and is sent from device to the carrier once a connection is established. Additional data stored in these log files are phone numbers and specific keyword data. The files are then loaded into memory and deleted off the disk once accessed. Outside of the logging of phone numbers connected to the network, it will also register calls made from devices as well.

MESSAGETAP will then utilize the open source libpcap library to intercept all targeted traffic to and from the server, where it will then exfiltrate the targeted variables off the machine for later analysis. Finally, it will seek to intercept SMS messages checking against a blacklist of IMSI numbers alongside using specific keywords to determine if the SMS messages contain specific text that are hostile to the Chinese government. If these keywords are found, the file will be logged elsewhere to the system for later exfiltration.


How widespread were these attacks?

Spread is limited to targeted attacks in the telecom vertical.


Are these recent attacks?

According to FireEye, this attack was first discovered in August of 2019.


What operating systems are affected?

Linux based systems, specifically those acting as Short Message Service Center (SMSC) servers.


What is the status of AV and IPS coverage?

Fortinet customers running the latest definition set are protected against this threat with the following AV signature:

ELF/Messagetap.A!tr


Any suggested recommendations or mitigations?

The FortiGuard SE team recommends that all AV and IPS definitions are kept up to date on a continual basis, and to always maintain a proactive patching routine when vendor updates are available. If it is deemed that patching is not feasible at this time, it is recommended that a risk assessment is conducted to determine additional mitigation safeguards within an environment.

Also, the FortiGuard SE and FortiGuard Labs teams are proactively monitoring the threat landscape for the latest announcements made by researchers through the responsible disclosure process or elsewhere to ensure that customers are protected with latest mitigation strategy and signature updates affecting the threat ecosystem.


Definitions

Traffic Light Protocol

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

TLP: RED

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.

TLP: AMBER

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.

TLP: GREEN

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.

TLP: WHITE

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.