APK malwares can not be uploaded to comodo server

Please fix it.


You can download the sample from the comment.

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Sure they can.
The same way one does with PC malware: zip it up first.
There are several good archive apps for Android. Use them.

still upload failed

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Can security apps block this kind of malwares? (no root)

“sending short messages in the background”

Without Root, no. At least what I have seen on my phone. (just upgraded to the S5, SM-G900W8: not rooted yet).