Some Android smartphones in the U.S. have a secret backdoor that sends data, including text messages, to China every 72 hours, according to a new report in The New York Times. Security contractors have reportedly found preinstalled software in some of the devices. The software allegedly monitors users’ travels and text messages. Authorities say it is unclear whether Chinese officials are using the stolen data for advertising or for more nefarious intelligence purposes. Those most vulnerable to the affected phones are international customers and customers with prepaid phones. Shanghai Adups Technology Co., the Chinese firm that wrote the software, says its code runs on more than 700 million phones and other smart devices.