Darkhotel APT Uses Hacking Team Exploit to Target Specific Systems

The Darkhotel advanced persistent threat (APT) group remains active. Researchers have uncovered this year new victims, new attack techniques, and new exploits.

The activities of the Darkhotel APT were detailed by Kaspersky Lab in November 2014. The group has targeted organizations from across the world, with victims identified in sectors such as the defense industrial base, military-related organizations, energy policy makers, governments, NGOs, large electronics manufacturers, pharmaceutical companies, and medical providers.

The threat actor, which appears to be Korean speaker, has used P2P torrents and highly customized spear phishing to deliver malware to victims. One interesting technique used by the cyber spies to install malware on the computers of business travelers in the Asia-Pacific region involved hacking hotel Wi-Fi networks.

According to Kaspersky Lab, the organizations targeted by the group in 2015 are located in North Korea, Russia, South Korea, Japan, Bangladesh, Thailand, India, Mozambique and Germany.

In April, researchers noticed that Darkhotel’s phishing emails contained links to Flash Player exploits discovered in 2014. However, at the beginning of July, the group started leveraging a zero-day whose existence came to light following the breach suffered by the Italian spyware maker Hacking Team.

“It looks like the Darkhotel APT may have been using the leaked HackingTeam Flash 0day to target specific systems,” Kaspersky’s Global Research & Analysis Team wrote in a blog post.

The espionage group has been using obfuscated HTML Application (HTA) files to deploy backdoor and downloader code on infected systems for several years now. In 2010, the attackers planted malicious code in such files in operations aimed at North Korea-related targets. This year, researchers spotted new variants of malicious HTA files.

“It’s somewhat strange to see such heavy reliance on older Windows-specific technology like HTML applications, introduced by Microsoft in 1999,” experts noted.

The spear-phishing emails sent out by Darkhotel contain .rar archives that appear to hold a harmless-looking .jpg file. In reality, the file is a .scr executable that is made to look like a JPEG using a technique known as right-to-left override (RTLO). When the file is opened, an image is displayed in the Paint application, while a piece of malware is executed in the background.

If in the past the group used a long list of weakly implemented, broken digital certificates, Darkhotel now appears to have a stockpile of stolen certificates that it uses to sign backdoors and certificates.

“Darkhotel now tends to hide its code behind layers of encryption. It is likely that it has slowly adapted to attacking better-defended environments and prefers not to burn these stolen digital certificates,” Kaspersky said.

In addition to improved obfuscation techniques, the attackers are also using more efficient evasion methods. For example, one of the signed downloaders analyzed by experts is designed to check the infected system for processes associated with known antivirus solutions.