A proof-of-concept system designed to detect remote-access Trojans (RATs) using only network data uncovered infections at companies in a variety of industries, according to a report released this week by information analysis firm Recorded Future.
Using only network scans and metadata collected between Dec. 2, 2018, and Jan. 8, 2019, Recorded Future uncovered 481 command-and-control (C2) servers used by attackers to manage computer systems compromised by 14 different families of RATs. In the report, which focused on three particular Trojans — Emotet, Xtreme RAT, and ZeroAccess — the company found nearly 20 command-and-control (C2) servers managing Emotet infections, more than 30 managing ZeroAccess infections, and nearly 70 managing xTreme RAT infections.
The detected servers only comprise a fraction of the total remote-access threat on the Internet because the technique cannot find every server, says John TerBush, senior threat researcher with the Insikt Group at Recorded Future. Still, the hundreds of C2 servers indicate a large problem, he stresses.
"There are a lot of RAT types out there that are quite successful," he says. "They can be pretty good at evading security detections through a variety of ways. They are not something that will be easy gotten rid of unless you are at the top of your game."
The detection of hundreds of C2 servers for RATs highlights the continuing threat and how far online attackers have infiltrated corporate networks. Once attackers have compromised a single system inside a network, they have a beachhead from where they can steal data, install additional functionality, or infect other systems.
"They create pivot points in your environment," TerBush says. "They can sit there and gather information from the host you are on, they can download other files, or they can use it as a pivot point for lateral movement. Some of them are simpler than others and not as useful, but there are a lot of variants with a lot of functionality."
The 19 servers managing Emotet, for example, communicated with infected systems in at least 26 organizations, mainly in Latin America, Recorded Future stated in its report. The RAT, originally discovered by security firms in 2014 when it delivered banking malware, now focuses on a variety of industries, such as automative, energy, construction, retail, and utilities. The focus on Latin America is a contrast to the first half of 2018, when Emotet mainly focused on targets in the United States.
Emotet evolved in 2018, moving from a RAT focused on the banking sector to a program that is used as a first-stage infector, which then can drop a variety of different modules onto a system.
Emotet is the most recently developed malware of the three on which Recorded Future focused the report. Both the Xtreme RAT and ZeroAccess malware are about a decade old, but they are still very popular. In its "2018 Botnet Trends" report, for example, network-security firm Fortinet found ZeroAccess to be the third most popular botnet on the Internet for the year.
Overall, security firms are finding that Trojans have more than doubled in the past year. While attackers use the infected networks for their own schemes, they also often install other groups' malware as a service or just sell the ability to access corporate servers to nation-states and other aggressors.
The capability to find RATs using network metadata could help companies detect further threats in their networks. While TerBush would not further detail Recorded Future's "secret sauce," a technique using only network scans and metadata would allow firms to more easily identify and block malicious network traffic.
TerBush stressed that the technique is not comprehensive but finds more than the low-hanging fruit.
"There is some proprietary data that is public network metadata that then gives us a bunch of IPs that are then connecting to those command-and-control servers," he says. "So we can specifically identify what is likely — it's hard to get 100% certainty — but what is likely based on port, connectivity, and time and that sort of thing likely installs connecting to the command servers."
As part of the report, Recorded Future released the IP addresses of the C2 servers and the indicators of compromise for the RATs. The company recommended that firms look for communications to those IP addresses in their logs.
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