Right now attackers are taking advantage of the game’s popularity and Android users despair to spread malware posing as an Android version of Super Mario Run as they did in the past for Pokemon GO. The trojan is called Android Marcher and has been around since 2013, mostly targeting mobile users financial information. After installation, the application attempts to trick users with fake finance apps and a credit card page in an effort to capture banking details. The malware also locks out Google Play until the user supplies their credit card information.
In this new variant of Marcher, it can monitor the device and steal login data of regular apps, not just banking and payment apps, and send the stolen data back to command and control (C&C) servers. Facebook, WhatsApp, Skype, Gmail, the Google Play store are all vulnerable. Criminals can exploit these stolen accounts to carry out additional fraud.
Zscaler researchers advice is:
To avoid becoming a victim of such malware, it is a good practice to download apps only from trusted app stores such as Google Play. This practice can be enforced by unchecking the “Unknown Sources” option under the “Security” settings of your device.
We may add to turn on “App Verification”. Verify Apps regularly checks activity on your device and prevents or warns you about potential harm. Verify Apps is on by default, as is Unknown Sources turned off. Verify Apps also checks apps when you install them from sources other than Google Play. Of course, there is a privacy trade-off. Some information has to be sent about the apps you install back to Google.
The main advice is: use common sense. It’s common practice for companies to release official apps versions through Google Play and highly unlikely to do it via any other way.
This was both an amusing and frightening talk. [Sam Bowne] presented How to Trojan Financial Android Apps on Saturday afternoon at the LayerOne Conference. [Sam] calculates that 80-90% of the apps provided by major financial institutions like banks and investment companies are vulnerable and the ease with which trojans can be rolled into them is incredible.
[Sam] did a great job of concisely describing the circumstances that make Android particularly vulnerable to the attacks which are the subject of the talk. Android programs are packaged as APK files which are easy to unpack. The “compiled” code itself is called smali and is readable in a similar way as Java. It’s super easy to unpack and search this byte code using grep. Once the interesting parts are located, the smali code can be altered and the entire thing can be repackaged. The app will need to be resigned but Google doesn’t control the signing keys so an attacker can simply generate a new key and use that to sign the app. The user still needs to install the file, but Android allows app installation from webpages, email, etc. so this isn’t a problem for the bad guys either.
So what can be done? This is about information harvesting. [Sam’s] proof of concept uses a python script to insert logging for every local variable. The script looks at the start of every module in the smali code, grabs the number of local variables, increments it by one and uses this extra variable to write out the values through logcat.
He demonstrated live on the Bank of America app. From the user side of things it looks exactly like the official app, because it is the official app. However, when you register your account the log reports the card number as you can see here. Obviously this information could easily be phoned-home using a number of techniques.
As mentioned, the vast majority of banking and financial apps are vulnerable to this, but some have made an attempt to make it more difficult. He found the Bancorp app never exposes this information in local variables so it can’t just be logged out. However, the same trojan technique works as a keylogger since he found the same function kept getting called every time a key is pressed. The same was true of the Capital One app, but it echos out Google’s Android keymap values rather than ascii; easy enough to translate back into readable data though.
The Inability to Report Vulnerabilities
What is the most troubling is that none of these companies have a means of reporting security vulnerabilities. It was amusing to hear [Sam] recount his struggle to report these issues to Charles Schwab. Online contact forms were broken and wouldn’t post data and several publicly posted email addresses bounced email. When he finally got one to accept the email he later discovered another user reporting on a forum that nobody ever answers back on any of the Schwab accounts. He resorted to a trick he has used many times in the past… Tweeting to the CEO of Charles Schwab to start up a direct-message conversation. This itself is a security problem as @SwiftOnSecurity proves by pointing out that whenever @SamBowne Tweets a CEO it’s because he found a vulnerability in that company’s platform and can’t find a reasonable way to contact the company.
There is Hope
Although very rare, sometimes these apps do get patched. The Trade King app was updated after his report and when [Sam] tried the exploit again it crashes at start-up. The log reports a verification failure. This indicates that the injected code is being noticed, but [Sam] wonders if the verification is included in the app itself. If it is, then it will be possible to track it down and disable it.
This may sound like all of us Android users should despair but that’s not the case. Adding verification, even if it’s possible to defeat it, does make the apps safer; attackers may not want to invest the extra time to try to defeat it. Also, there are obsfucators available for a few thousand dollars that will make these attacks much more difficult by making variable names unreadable. The free obsfucator available now with the Android development suites doesn’t change names of everything… local variables are left unaltered and programmers have a habit of using descriptive names for variables. For instance, BofA used “CARDNUM” in the example above.
[Sam Bowne’s] slides and testing results for the entire talk are available under the “Upcoming Events” part of his website.
The Polytechnic Institute of NYU is hosting an interesting embedded systems contest. They’ve constructed a solid state cryptographic device that uses a 128-bit private key. Contestants will be tasked with designing and implementing several trojans into the system that will undermine the security. The system is built on a Digilent BASYS Spartan-3 FPGA board. The trojans could do a wide variety of things: transmitting unencrypted, storing and transmitting previously entered plain text, or just shutting down the system entirely. The modified devices still need to pass the factory testing procedure though, which will measure power consumption, code size, and function. After a qualification round, participants will be given the necessary hardware to compete.
The Zlob trojan, also known as DNSChanger, has been around for a few years, but recent Zlob variants to appear in the wild attempt to log into routers using a list of default admin/password combos. If they succeed, they alter the DNS records on the router to reroute traffic through the attacker’s server.
Our friend [Dan Kaminisky] recently did a presentation warning against vulnerabilities in internet browser plugins that allow attackers to mount DNS rebinding attacks against routers with default passwords.. Though it achieves the same end, Zlob is different because it infects by the tried-and-true method of fooling users into downloading it inside a fake video codec. Once it is running on a client machine, it is free to attempt to use the default admin id and password of the router to log in and alter DNS settings. It even supports the DD-WRT firmware.
Even if a system is wiped clean of Zlob trojans, the router could still be compromised. The good news is that it is easy to fix and even easier to prevent. Fixing it takes no more than wiping all network clients clean, then resetting the router and restoring custom settings. Prevention is a simple matter of changing the router’s password.