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Threats From “Free” Android Apps in Japan (Part 2)


Smartphone users in Japan are able to download a wide variety of apps, many of which are either inexpensive or free. Not all of these actually meet what users expect in terms of features, and some even introduce risks that users may not fully understand. In this blog entry, I will report the privacy risks caused by certain apps that we have looked into.

The Ad Delivery Cycle for “Free” Apps

As mentioned in the first entry, we define those apps that demonstrate the following routines without user consent as high-risk apps (referred as “ego apps” in Japan):

  • Displaying pop-up ads
  • Getting the user’s private information

One reason these apps are significantly increasing lately is the way that ads are sold in Japan.

As you can see in this graph, these ad agents/networks provide software development kits (SDKs) for app developers. By inserting the SDK-provided code into their apps, app developers can have ads appear inside their apps. They would then earn money from how many ads are viewed and/or clicked. This revenue allows the developer to charge little or no money for his app.

However, users put their personal information at risk when they download these apps. Users may be able to afford many free or cheap apps, but they may fall victim to ad networks that may not show a EULA or even get their private information without consent. If these privacy-violating apps increase in number, users would be at increased risk of information theft.

How to make the Ads Safer

One benefit of ads in mobile apps is that it allows independent app developers to earn money. In addition, it also allows what would normally be expensive apps to be sold with a low (or no) price at all. Imposing a blanket ban of advertising and acquiring user information may be harmful to the mobile sector as a whole.

So how can we make ad-supported apps safer for everyone? First, users should know that it is a good idea to check if the app they are downloading is reputable. To do this, users can check the comments of the app they want to download, as well as other apps offered by the developer.

App developers may also want to make it easier for users to find and read their EULA, their privacy policy, and the permissions their apps require. Aside from making these documents easier to find, the content should also be similarly easy to read and understand. An example of how this can be done is Trend Micro’s own app:

The Ministry of Internal Affairs and Communication (MIC) has issued guidelines for Japanese app stores and developers that list the eight items that should be included in privacy policies. Seeing if all eight are present would be a good way to know whether or not the privacy policy of user’s app is really legitimate. MIC is not alone in these type of efforts; both telecom trade groups like the GSM Association and governments like the United States have released similar guidelines.



The Developer ‘s Name Indicate the full name of the app developer and contact address.
User Information Type Enumerate all types and contents of the user information extracted.
Method Indicate how to extract the information – if it is through user’s own input or if it is automatically acquired.
Purpose Indicate if it is used for further services to users or for other purposes. If it is used for the ad-delivery or marketing purposes, indicate this.
Notice / User Involvement Indicate how to release the notice, how to get the agreement, how and where to post the privacy policy, who are the target users to get the agreement, and when these are conducted.
The Third-Party Providers,  External Senders, and Info-gathering Modules Indicate if it contains such items as the third-party providers, external senders, and info-gathering modules.
Contact Details Indicate the contact details such as phone numbers, email addresses, etc.
Change Procedure Indicate the procedure when the privacy policy is changed.

Table 1: MIC Guidelines for the Privacy Policy

Our Investigation

To evaluate the risk to user privacy, we looked at the 200 most popular free apps (both general apps and gaming apps) in the Google Play app store in Japan as of August 31, 2012.

Using the top 200 of the most popular apps (respectively both general apps and game apps) out of all free apps in Google Play Japan according to Google’s announcement as of August 31, 2012, Trend Micro evaluated the risk of privacy violation on these sample apps.  The details of the sampled data are indicated in both table 2 and 3.

Location Google Play – Japan
# of APK Files 400
Targeted Categories Google Play-Applications, FreeGoogle Play – Games, Free
Date Covered August 31, 2012
Sampling Criteria Top 200 of the most popular apps (respectively both general apps and game apps) out of all free apps in Google Play Japan according to Google’s announcement as of August 31, 2012

Table 2: The Details of the Examined Apps

We used Trend Micro Mobile App Reputation (MAR) to examine these apps, looking at three areas in particular:

  • unwanted routines
  • information leakage (focusing on privacy violations)
  • high memory usage

Based on our analysis, we grouped the apps into four categories, from highest to lowest risk, namely: “Malicious”, “High Risk”, “Low Risk”, and “Safe”.

As you can see above, 0.5% (one app) of all general apps and 1% (two apps) of all game apps are considered “malicious”. 5% of all general apps and 3% of all game apps are considered as “high risk”. More “high risk” apps are present among general apps than gaming apps.

Apps considered as “Malicious” have unwanted routines like delivering malicious ads. App developers should be careful about which ad network they use, as if their apps is found to contain malicious apps, their reputation may be damaged. The same is true if their app leaks personal information.

The above chart shows the types of personal information that is acquired by the studied apps. This information was also used in rating the risk level of apps.

Trend Micro Mobile Security (known as Virus Buster Mobile for Android in Japan) has a function known as “Privacy Scan”. With this, users can easily check the privacy risks of their installed apps. It can also scan apps as they are being installed; users can also check the already-installed-apps manually to check their privacy risks.)

If the scan results make you feel suspicious about the possibility of a privacy leak, check the comments on its download page, as well as its EULA and privacy policy. If these convince you that the app is legitimate, continue – but if in doubt, uninstall.

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