SAN FRANCISCO — The Justice Department unsealed an indictment of two Chinese nationals on Thursday, charging them with the 2014 hack of the insurance company Anthem and attacks on three other, unnamed American businesses the next year.

The charges were the latest in a string of aggressive moves by American officials who say they are trying to crack down on theft of trade secrets and personal data by China.

A federal grand jury in Indianapolis, where Anthem is based, charged Fujie Wang, 32, of Shenzhen, China, and an individual indicted as John Doe with conspiring to commit fraud, wire fraud and intentional damage to a protected computer.

The indictment says the two targeted employees of an Anthem subsidiary and at least three other companies with so-called spear-phishing emails beginning on Feb. 18, 2014. Less than a month later, the indictment says, the hackers got inside Anthem’s network and searched through troves of personal data.