About 1.5 billion users worldwide install WhatsApp programs to communicate with people on their mobile phones. WhatsApp recently confirmed that a hacker organization exploited a vulnerability in the WhatsApp program to install a monitor on particular users’ phone. According to foreign media reports, the intrusion program was developed by an Israeli network intelligence company. The intruder will try to call the target user via WhatsApp. As long as it successfully connects to target’s WhatsApp, it will use vulnerability to install the monitoring software into the phone, regardless of whether the user has answered it or not. WhatsApp says that the intruder is targeted at specific users, but it has not yet been confirmed how many users are affected. WhatsApp has fixed the vulnerability and called on all users to update the program as soon as possible, to make sure they are protected.