Citizens need to be vigilant and patch poorly secured wireless networks, the Indian police said Monday after announcing the arrest of technology-savvy members of a militant group that exploited insecure wireless networks to send messages.

The suspects, part of the militant group Indian Mujahideen, sent e-mail claiming responsibility for serial bombings in the major Indian cities of Delhi and Ahmedabad prior to explosions in July and September, the Indian police said during a news conference.

Roaming around Mumbai with Wi-Fi detectors, the suspects looked for open Wi-Fi signals and programmed the e-mail messages to be sent from hacked wireless networks prior to the blasts, the Indian police said.

The technique used by the militants is similar to "wardriving," where hackers roam around to detect and access Wi-Fi networks with security weaknesses.

India has recently witnessed a spate of serial bomb blasts that has put the country in a state of alert. Blasts in major cities, including IT capital Bangalore in July, have taken hundreds of lives.

Among those suspected of having a hand in sending e-mail messages were engineers working for multinational firms, though the police did not name any companies. One person, Mohammed Asghar Mansoor Peerbhoy, earned around 1.9 million rupees (US$40,550) annually working as a software engineer for a multinational firm, police said.

Five laptops, three pen drives, wireless routers and radio frequency detectors were recovered from the suspects, the police said.

An e-mail sent by the group on Sept. 13 said that Delhi was about to be hit with blasts and that the militant organization would strike other locations in India. The e-mail, sent to top news organizations in India, was from a Yahoo e-mail account that was traced to an insecure wireless network in suburban Mumbai.

The group also claimed responsibility for Ahmedabad blasts five minutes prior to the 21 serial bomb blasts that rocked the city July 26. The e-mail address was ultimately tracked to the insecure Wi-Fi account of Kenneth Haywood, a U.S. executive working for a firm in Mumbai. Haywood fled for the U.S. after feeling the heat of being at the center of the investigation by Indian authorities. He returned after his name was cleared.

The IDG News Service is a Network World affiliate.