The results give some unexpected results. Only the app Threema evaluate by the tester as non-critical where as WhatsApp itself is classified as very critical one in data protection, as well as the BlackBerry Messenger and Line also categorize as very critical and the same for the Telegram. According to Stiftung Warentest; they have checked the messenger in the Android and iOS versions of the Messenger, and they checked whether the apps encrypt user data and what information they transmit to whom.
However one complaint is there are that Threema is not open source software. Therefore, a complete analysis according to Stiftung Warentest has not been possible. However, the same applies for all other tested apps. Even in the partly open source Telegram was not possible a full review of the transfer. The fact that data regarding the telegram sent unencrypted, but was ruled out, writes the consumer organization. The Messenger WhatsApp was described by the critics as very critical, unsurprisingly. The app was noticed in recent months repeatedly by security flaws.
According to Stiftung Warentest the Android version itself sends unencrypted data that the user enters including interview content might be. The tester feared that by many of the user data of WhatsApp transfer to the servers of Facebook. From the terms of the app, it is apparent that "the users data can be passed on to the new owner, i.e. Facebook.
Facebook had announced the purchase of WhatsApp last Thursday. The other two Messenger, Line, and BlackBerry Messenger, were mentioned as critical by the consumer organization with respect to the data protection. The Android app of line sends the serial number IMEI of the device unencrypted to third parties further criticized by the tester. Blackberry on the other hand could create accurate personality profiles even with the data of its users.