Chinese Android App Acts Like Trojan to Stealthily Record Mobile Calls
Researchers recently uncovered a new Android app sold in Chinese app stores that has the capability to surreptitiously record phone conversations.
Once installed on the victim's Android device, the app downloads a "configuration" file containing the parameters for a remote server and proceeds to record and store phone conversations entirely without the phone owner's knowledge, Dinesh Venkatesan, a researcher with CA Technologies, wrote in the company blog Aug. 2. The recordings, in AMR format, are saved onto the device's SD card and can be played back on software such as VLC Media Player, Venkatesan said.
Researchers have warned eWEEK in the past that voice-recording malware could be used to capture account passwords, credit card numbers and social security numbers that consumers may say while talking with customer service representatives on the phone.
This type of functionality has been seen before in commercial spyware, Ciaran Bradley, vice president of handset security at Adaptive Mobile, told eWEEK.
Venkatesan tested the app in a "controlled environment with two mobile emulators running simulated Internet services," according to the blog post. Unlike an Android Trojan that CA Technologies recently analyzed, which logs the numbers of incoming and outgoing calls and the call duration into a text file, this app "is more advanced," Venkatesan wrote.
Symantec researchers pointed out that while the app may be used for nefarious purposes, the creator of the app is being quite upfront about the capabilities. The app, found on unofficial Chinese app stores, is listed as a way for jealous spouses to monitor their significant other's phone conversations for hints of infidelity, said Irfan Asrar, an analyst with Symantec Security Response. It is also not very stealthy because after it is installed on a user device by someone else, the owner can easily tell by looking at the screen that a call is being recorded.
While Venkatesan didn't observe it directly, the configuration file hinted at an ability to upload the recorded calls from the SD card to a remote server. Symantec's Asrar did not find that to be the case in Symantec's own analysis, saying that a physical access to the device was required to retrieve the files. The app did have the ability to send data such as GPS location and logs to the remote server, which "the suspicious husband or wife" would have to pay to see a copy of, Asrar said.
This call-recorder needs user intervention, most likely by the spouse who has commandeered the device, before it can be installed. So there is a security risk of users having recording software installed without their knowledge.
Intentionally malicious or not, the app definitely has the potential to be used as a Trojan. Even though it displays a legitimate permissions screen stating what device capabilities it needs access to, such as audio recording and outgoing call interception, users rarely think twice about what the app is capable of doing, according to Bradley.
Despite being PC-security savvy, users tend to consider the mobile environment "safe" and not think twice about install prompts, links in instant messages and SMS messages and other threats, Bradley said. Criminals are betting that the average mobile user will install apps without thinking twice. "The criminals may very well win this type of bet," Bradley said.
A recent study from Lookout Security suggested Android users are 2.5 times more likely to be affected by malware today than they were six months ago.
"As it is already widely acknowledged that this year is the year of mobile malware, we advise the smartphone users to be more logical and exercise the basic security principles while surfing and installing any applications," Venkatesan wrote.