Security researchers including from Straya's own CSIRO have studied 283 VPN apps for Android and found big problems with many of these applications.
Some findings: 84% of them leaked traffic data via IP6, 66% of them leaked DNS data, 75% used third party tracking services and 18% didn't encrypt communications at all. Great stuff.
These applications are hosted by Google's Play service. 38% of them contained malicious code according to Virustotal, a Google owned service. So if you were wondering if Google's terrible attitude to security on Android is changing there's your answer.
Services called out as "malicious or intrusive": EasyOvpn, VPN Free, Tigervpns, DNSet, CM Data Manager, Rocket VPN, Globus VPN, Spotflux VPN and CyberGhost.
Services flagged up as containing malware in the VirusTotal database: OkVpn, EasyVpn, SuperVPN, Betternet, CrossVpn, Archie VPN, HatVPN, sFly Network Booster, One Click VPN, and Fast Secure Payment.
Using home broadband connections (possibly hacked computers) as egress points: Open Gate, VPN Gate, and VyprVPN
Tigervpns, StrongVPN, and HideMyAss raised suspicions after exogenous traffic was spotted from them.
One service they recommended was F-Secure Freedome VPN which unfortunately costs $50 per year so no one will use it.
http://www.theregister.co.uk/2017/01/28/vpn_on_android_means…
https://arstechnica.com/security/2017/01/majority-of-android…
So what about Open VPN then? I've been using that for almost 3-4 years.