Security experts have warned that smartphones running on AT&T and at least 47 other carriers are vulnerable to hijacking. iPhones and Android devices are particular targets for malicious hackers, who can intercept information and phone calls as well as text messages.

As the researchers from the University of Michigan's Computer Science and Engineering Department found out, hackers use Internet connections to attack smartphones. They can inject vicious codes into unencrypted Facebook and Twitter pages in order to make the targeted device perform unintended actions by the users.

The hijacked smartphones can post messages and follow new Twitter users. "It breaks the common assumption that communication is relatively safe on encrypted/protected WiFi or cellular networks that encrypt the wireless traffic,"  explained the computer scientists in a research note.

"In fact, since our attack does not rely on sniffing traffic, it works regardless of the access technology as long as no application-layer protection is enabled," added the researchers.

The US carrier mentioned in the research study, AT&T, issued a press release stating that the report doesn't provide enough data to warrant a worrying conclusion, and would investigate the matter further.

The issue of hackers targeting smartphones is not new, as previous reports reveal.