A threat actor believed to be operating out of China has been targeting physically isolated military networks in Taiwan and the Philippines, Trend Micro reports.
Tracked as Tropic Trooper and KeyBoy, and active since at least 2011, the threat actor is known for the targeting of government, military, healthcare, transportation, and high-tech industries in Taiwan, the Philippines, and Hong Kong.
Previously, the group was observed targeting victims with spear-phishing emails containing malicious attachments designed to exploit known vulnerabilities, such as CVE-2017-0199.
Now, Trend Micro reveals that, since December 2014, the threat actor has been leveraging a piece of malware referred to as USBferry to target entities such as military/navy agencies, government institutions, military hospitals, and even a national bank.
USBferry is a piece of stealthy USB malware capable of executing various commands on specific targets, and designed to steal critical data through USB storage.
To ensure the success of their attacks, the hackers would first target organizations related to military or government, which might employ less robust security, and use these as jumping-off points for attacks. In one instance, the group compromised a military hospital and used it to move to the military’s physically isolated network.
USBferry was initially mentioned in a 2017 PricewaterhouseCoopers report, but without a technical analysis. Trend Micro’s investigation into the malware revealed the use of at least three versions, each with different variants and components.
The activities the malware performs on the compromised systems differ from one environment to another: it can execute commands, source target files or folder lists, and copy files from air-gapped machines to compromised hosts.
“The group achieves infection by employing the USB worm infection strategy and ferrying a malware installer via USB into an air-gapped host machine,” Trend Micro explains.
The malware checks for network connectivity and, if none is found, it proceeds to collect information from the machine and copy the data to the USB drive.
The security researchers also discovered that the hackers have employed several different backdoors in a recent incident, including WelCome To Svchost (the first version dated 2011), Welcome To IDShell, and Hey! Welcome Server.
Other tools the hackers have employed in their attacks include a command-line remote control listener/port relay tool, backdoor payload/steganography payload execution loaders, and port scanning tools available on the Internet.
The group was also observed using steganography to mask backdoor routines and evade anti-malware and network perimeter detections. The technique was used to send information to the command and control server, in addition to delivering payloads.
“Tropic Trooper seems to have been targeting air-gapped environments over the past six years; in particular, the group prefers to target military hospitals and national banks as initial footholds. It could be difficult for some military and government offices to have sufficient security controls; protections can be challenged and thus make incident response trickier,” Trend Micro notes.