Organizations in the healthcare sector continue to be the main targets of the Gatak Trojan, a piece of malware that can steal information and perform backdoor functions, Symantec researchers warn.
Also known as Stegoloader and targeting mainly enterprise networks, Gatak (Trojan.Gatak) has been around since 2011, primarily focusing on organizations in the United States. Spreading through websites that promise licensing keys for pirated software, the malware hasn’t spared international organizations either, and the healthcare sector has suffered the most.
While the majority of the machines infected by this Trojan (62%) are located in enterprise environments, 40% of the top 20 most affected organizations are from the healthcare sector, Symantec says. Previously, however, the threat actors behind the malware have focused on the insurance sector as well.
Gatak spreads bundled with product keys for pirated software, via dedicated websites. The attackers lure victims by supposedly offering product keys for software usually used in professional environments, but the keys don’t work and users end up infected. The legitimate versions of these applications aren’t compromised, since the websites used by attackers aren’t connected with their developers.
Some of the programs used by the Gatak gang as lures include SketchList3D (woodworking design), Native Instruments Drumlab (sound engineering), BobCAD-CAM (metalworking/manufacturing), BarTender Enterprise Automation (label and barcode creation), HDClone (hard disk cloning), Siemans SIMATIC STEP 7 (industrial automation), CadSoft Eagle Professional (printed circuit board design), PremiumSoft Navicat Premium (database administration), Originlab Originpro (data analysis and graphing), Manctl Skanect (3D scanning), and Symantec System Recovery (backup and data recovery).
The malware has two main components: a lightweight deployment module that gathers information on the infected machine and can install additional payloads; and the main module, a fully-fledged backdoor Trojan designed to steal information from the infected computer and achieve persistence.
Gatak authors also use steganography to hide data within image files, and the malware attempts to download a malicious PNG image immediately after installation. The image contains an encrypted message with commands for the Trojan and files to be executed.
The malware also attempts lateral movement in the compromised environments, and researchers noticed that in 62% of cases this occurs within two hours of infection. Researchers believe that this function isn’t automated but carried out manually, while also suggesting that the attackers might not have the resources to exploit all infections immediately or they could prioritize targets.
Most likely, researchers say, the attackers move across an organization’s network by exploiting weak passwords and poor security in file shares and network drives. No evidence of zero-day exploits or sophisticated hacking tools being used has emerged so far, but the attackers were seen infecting computers with other malware, including ransomware and the Shylock (Trojan.Shylock) financial Trojan.
The Gatak threat group is said to be cybercriminal in nature, given the absence of zero-day exploits or advanced malware modules, although they focus on enterprises and their malware has capabilities to support more traditional espionage operations. The attackers are opportunistic, given the distribution method, which shows that they are largely passive, lacking control over who is infected.
It’s also unclear how the attackers monetize on their attacks, but Symantec suggests that they could be selling the personally identifiable information (PII) and other data they manage to exfiltrate from the infected machine. This would also explain their focus on the healthcare, as these records are priced higher than other personal information.
“Healthcare organizations can often be pressurized, under-resourced, and many use legacy software systems that are expensive to upgrade. Consequently, workers could be more likely to take shortcuts and install pirated software. While organizations in other sectors appear to be infected less frequently, the attackers don’t appear to ignore or remove these infections when they occur,” Symantec says.
The security firm notes that Gatak represents a reminder that the use of pirated software can compromise the security of an organization in addition to creating legal issues. It is important for companies to regularly audit the software used on their networks, as well as to educate their employees about the dangers of using pirated or unapproved applications.