Mobile botnets show their disruptive potential

Mobile botnets show their disruptive potential. DENIAL-of-services (DoS) attacks are a common tactic used by "black hats" intent on bringing down a high-profile website, one owned by a bank or political party, say. But what if these hackers now have cellphone networks in their sights?

In a standard DoS attack, a network of infected PCs, a "botnet", would swamp a server with so many requests to view a web page that it would be unable to handle legitimate requests. Now Patrick Traynor of the Georgia Institute of Technology in Atlanta and colleagues have shown how a cellphone network could be the vehicle for an attack that would cut off calls for millions of users.

Traynor and his team used software that simulates a cellular network's Home Location Register (HLR) - a massive database that stores the details of every SIM card an operator issues and would typically contain details on up to 5 million subscribers. Traynor found that a botnet of fewer than 12,000 infected cellphones could disrupt 93 per cent of traffic - voice calls and SMS messages - to a hypothetical HLR of 1 million subscribers. In a real-life attack the owners of infected handsets would be unaware that their phone was part of a botnot.

"Phones have evolved so quickly - we've gone from just the ability to make phone calls to many of the things that desktop computers can do," says Traynor. "As utility comes to this platform, we have to expect that malicious behaviour is going to follow pretty quickly."

Indeed, the first phone botnet is believed to have been assembled earlier this year after an SMS worm called "Sexy Space" cascaded across cellphone networks. Users who clicked on a link in the message had software installed on their handset that was capable of communicating with a central server, making it possible for their phone to be controlled remotely by a third party.

The first phone botnet was assembled earlier this year after an SMS worm hit cellphone networks

"These threats are certainly feasible. Whether they will be implemented by an attacker remains to be seen," says Zulfikar Ramzan of network security company Symantec. Ramzan points out that while smartphones are powerful, they are still not as attractive a target as PCs, which can be hijacked to send large amounts of spam or host malicious websites. He argues that while a mobile botnet might be used to bring down part of a cellular network, it's not clear how profitable such an attack would be. ( )

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