Internet phone systems: The latest entry point for cybercriminals

As the traditional telephone system becomes integrated with the Internet, new opportunities for fraud abound and attacks on the Asterisk VoIP system are 'endemic'

Cybercriminals have found a new launching pad for their scams: the phone systems of small and medium-sized businesses across the U.S.

In recent weeks, they have hacked into dozens of telephone systems across the country, using them as a way to contact unsuspecting bank customers and trick them into divulging their bank account numbers and passwords.

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The victims typically bank with smaller regional institutions, which typically have fewer resources to detect scams. Scammers hack into phone systems and then call victims, playing prerecorded messages that say there has been a billing error or warn them that the bank account has been suspended because of suspicious activity. If the worried customer enters his account number and ATM password, the bad guys use that information to make fake debit cards and empty their victim's bank accounts.

Hackers made headlines for breaking into phone company systems more than 20 years ago -- a practice that was known as phreaking -- but as the traditional telephone system has become integrated with the Internet, it's creating new opportunities for fraud that are only just beginning to be understood.

VoIP (voice over Internet Protocol) hacking is "a new frontier in the crossover world of telecom and cyber [crime]," said Erez Liebermann, assistant U.S. attorney for the district of New Jersey. "It is an ongoing threat and a serious threat that companies need to be worried about."

Attacks on one of the most popular VoIP systems, called Asterisk, are now "endemic," said John Todd, who works for the product's creator, Digium, as open-source community director. "It's like stealing a baseball bat to break into a car. The first step is to break into Asterisk."

Asterisk hacking began evolving from a fairly "low-level problem" into a much more serious issue around September of 2008, when easy-to-use tools were first published, Todd said. "There are now people doing videos on it and there are blogs and podcasts," he said. "The information is out there."

With these tools, it can be pretty easy to hack a VoIP system by hitting the server designed to connect traffic from the office's local area network to a network provider such as AT&T, which connects the calls to the rest of the world.

The hacker tries to guess the VoIP system's passwords, making thousands of guesses. While an Internet program such as Gmail will block visitors after a handful of failed password guesses, VoIP systems are often not configured this way and will often let any computer connect to them. So hackers pound away at them, trying to guess working phone extensions. Once they find an extension, they run their dictionary attack software. If the password is easy to guess, they're in the network and can phone out for free.

That's what happened to Innovative Technologies, based in Wheeling, West Virginia. It was hacked in early October, apparently by Romanian cyber criminals who used its VoIP system to make telephone-based phishing calls to customers of Liberty Bank, a small regional bank with offices in California.

"They had scanned a whole bunch of IP addresses on the Internet in order to find [VoIP] servers," said Terry Lewis, CEO of Innovative Technologies.

On Oct. 3, Lewis started getting voicemail from Liberty customers who had received the scam calls. He checked his VoIP system logs the next day and found that the hackers had made about 300 calls over the weekend -- not so many calls that it would normally have even been noticed.

Once the VoIP system is hacked, the criminals use it to perform phone-based phishing attacks, sometimes called vishing. Vishing attacks have been around for a few years now, but they've largely flown under the radar, because they often target smaller regional banks rather than high-profile national institutions. The scammers move from bank to bank each week after completing their campaigns.

According to Liberty Bank, other regional institutions have also been hit with vishing attacks from hacked VoIP systems in recent weeks.

Liberty did not name the other banks involved, but in recent weeks, Union State Bank and Solvay Bank have reported similar scams.

Lewis was lucky that he didn't get hit with major phone charges. Depending on how their systems are configured, businesses can be held responsible for any phone charges -- international call charges, for example -- that arise from the incident.

"If someone starts abusing your telephone system, you are potentially on the hook for a lot of money," Digium's Todd said.

Liberty Bank First Vice President Jill Hitchman believes that the scammers who targeted her bank probably hit between 30 and 35 businesses and were making between 20,000 and 30,000 phone calls per day. "I don't think these companies realize they're probably going to be getting charges," Hitchman said. "The bigger issue is, how are these phone systems being accessed and why can't we stop it?"

Only a few Liberty customers fell for the scam, Hitchman said, but the attackers knew what they were doing. First they would sign up for AOL accounts, to test that the card numbers worked. Because AOL offers free trial memberships, these charges do not show up for months. By that time, the scammers have put the information on fake ATM cards and emptied the bank accounts.

Businesses could prevent a lot of these attacks by changing the port they use for Session Initiation Protocol (SIP) connections on their VoIP systems, by blocking connections after a certain number of failures, and by simply using better passwords on their voice systems, security experts say.

The problem is that for most small and medium-sized businesses, security is just not a priority. "People care way more about whether their conference calls are going to have decent phone quality," said Rodney Thayer, chief technology officer with VoIP security company Secorix.

They don't think about their VoIP systems as vulnerable to Internet attacks just like Web or e-mail servers, and that's a mistake, Thayer said. "They think about it as a different system, and it's not," he said. "It's all the same stuff; it's all data going over a network."

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