Chinese APT Group Uses Hacking Team’s Flash Player Exploit

The Adobe Flash Player exploit stolen by hackers from spyware maker Hacking Team has been leveraged by advanced persistent threat (APT) groups, according to security solutions provider Volexity.

One of the groups observed leveraging CVE-2015-5119, which Adobe patched on Wednesday morning, is known as Wekby, APT 18, Dynamite Panda and TG-0416. The threat group, believed to have Chinese roots, is the main suspect in last year’s attack on Community Health Systems. Attackers stole 4.5 million patient records from the organization, reportedly by exploiting the OpenSSL vulnerability dubbed Heartbleed.

According to Volexity, Wekby launched a spear phishing campaign involving emails titled “Important: Flash update” just as Adobe was getting ready to patch the Flash Player zero-day.

The emails were sent out using a spoofed Adobe email address and they contained a link apparently pointing to the official Adobe download domain. Users who clicked on the link were taken to a website set up to serve a malicious SWF file designed to exploit the Flash Player vulnerability in order to deliver a piece of malware.

The malware, in this case the Gh0st remote access Trojan (RAT), communicates with a Singapore IP address that has served as a command and control (C&C) server in many of Wekby’s attacks over the past years.

Labels spotted by researchers in the malicious SWF file suggest that Hacking Team is the source of the exploit.

Volexity says the Flash Player exploit has been leveraged in multiple APT and non-APT attacks.

Hackers leaked a total of 400GB of data stolen from Hacking Team, including surveillance software, source code and exploits. The Flash Player exploit was integrated into exploit kits before Adobe managed to patch the vulnerability. Trend Micro reported that the Flash flaw was exploited before the Hacking Team breach came to light in attacks apparently aimed at users in Korea.

As far as Wekby is concerned, Volexity is not the only security firm to analyze the group’s activities recently. ThreatStream issued a report on Monday detailing some of the evasive maneuvers used by the threat actor.

Researchers discovered that the group has been using variants of the HTTPBrowser tool that uses DNS as a covert channel for communications. Experts also noticed that the APT actor has been trying to complicate the analysis of their malware by using return-oriented programming (ROP) to control execution flow.