A recently discovered mobile malware family called DressCode has infected over 400 applications that are being distributed via Google Play, Trend Micro security researchers warn.
The malware was initially said to have infected only around 40 apps in Google Play and a total of 400 apps distributed via third party app stores, but the actual infection numbers might be much higher, it seems. Over 3,000 apps distributed by several well-known Android mobile markets have been infected with this Trojan, security researchers say.
The malware has been stealthily spreading since April, and has been found in a wide variety of applications, including games, skins, themes, phone optimization boosters, and more. However, since the malicious code makes for only a small part of each Trojanized application, detection is rather difficult, Trend Micro says.
As soon as an infected app has been installed on a victim’s device, the malware connects with the command and control (C&C) server, which is a domain in the newer versions (it was a hardcoded IP address before). The device is then turned into a proxy that can relay traffic between the attacker and internal servers the device is connected.
“A background service creates a Transmission Control Protocol (TCP) socket that connects the compromised device with the C&C server and sends a 'HELLO' string to finish registering. Once the C&C server replies, a 'CREATE, <Attacker IP>, <Port>' command prompts the device to establish a TCP connection between it and the attacker. This allows the device to receive commands from the attacker via the SOCKS protocol,” Trend Micro explains.
According to the security researchers, the device initiates a TCP connection to the C&C server and another to the attacker, because it is behind a router. As soon as the SOCKS proxy has been set up, the device can forward commands from the attacker to other servers in the same LAN, thus allowing the attacker to connect to internal servers located behind the router.
By leveraging infected devices as proxies, the attacker exposes both the device owner and the network they are connected to. The actor can infiltrate the user’s network environment, which could pose a great risk to businesses, if the infected device is used within an enterprise network, researchers say.
In such scenarios, “the attacker can either bypass the NAT device to attack the internal server or download sensitive data using the infected device as a springboard. With the growth of Bring Your Own Device (BYOD) programs, more enterprises are exposing themselves to risk via carefree employee mobile usage,” Trend Micro says.
Because of the installed SOCKS proxy, the device can be abused as a bot if the attacker decides to ensnare them into a botnet, and can be used in various types of attacks, including distributed denial-of-service (DDoS) attacks or spam email campaigns. The attacker could generate revenue in other ways as well, such as creating fake traffic or disguising ad clicks.
Because infected devices can be used to reach other devices connected to the same network and because attackers can discover the IP address of these devices by exploiting weak router credentials or other vulnerabilities, the malware opens the door for other types of attacks as well. Connected cameras and other devices would be exposed to the attacker, the security researchers say.
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