Security researchers have found that 95% of Android devices running version 2.2 to 5.1 of operating system are vulnerable to a security bug. The vulnerability resides in a core Android component called ” Stagefright,” a multimedia playback library used by Android to process, record and play multimedia files such as PDFs. All a hacker needs is the phone number of the victim’s Android device. The hacker could then sends the malicious message that will surreptitiously execute malicious code on the vulnerable device without the owners being aware of it.
Source: https://thehackernews.com/2015/07/android-phone-hacking.html