I've noticed a curious oddity with some traffic sniffing from my apps on my iPhone. I've installed the ZAP Proxy CA certificate on the device, but I've noticed I can sniff some app traffic, and others I can't. This was apparent six months ago, but I've observed now even more of my suite failing to connect via the proxy, so my presumption is a trusted certificate is no longer trusted.

I'm aware there was an issue with iOS whereby a library permitted untrusted certificates to be used, but surely if I've installed a root CA, explicitly told the device its trusted, then I should be able to view all HTTPS traffic from the device?

Failing this, is it still possible to sniff HTTPS from the device via a proxy?

1 Answer 1


Yes, it is generally still possible, but techniques like Certificate Pinning and others make it more and more difficult to do a Man-in-the-Middle Attack.

I've also observed quite a lot of apps (on Android though) and found that especially messaging and communication apps (Facebook, Snapchat, ...) try to make sniffing network traffic as hard as possible.


You could try to disable Certificate Pinning on your device / browser. This is easy for desktop systems (@Psiinon linked to a guide How-to disable certificate pinning in Firefox - thanks for pointing this out).

For disabling certificate pinning on smartphones, you need to root / jailbreak the device. A tool for iOS might be SSL Kill Switch 2, and for Android one could use JustTrustMe (root and xposed required).

I have tried neither of the tools listed above. Both tools are listed in this presentation by Anant Shrivastava. See slides 15 and 20.

Last note: Disabling a security feature like certificate pinning is a security threat and is only recommended for testing.

  • Thanks Lukas! Its for testing only, and I am aware of the security implications. I will try find an older device to jailbreak and unpin the certificates.
    – Colin
    Commented May 10, 2016 at 10:52

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