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Call centers under attack in targeted cyber-blackmail scheme
Crooks blasting public-safety phone lines with calls
The US Department of Homeland Security (DHS) has cautioned public-safety call centers against the rise of so-called telephony denial of service (TDoS) attacks, which it says have the potential to cripple local telephone exchanges.
The warning was issued in March in a confidential Situational Awareness Update that was obtained by security blogger Brian Krebs, published jointly by DHS and the FBI.
In much the same way that a DDoS attack brings down a server by flooding it with requests, a TDoS attack works by bombarding an organization's phone numbers with calls, making it impossible for legitimate calls to get through.
According to the bulletin, DHS officials have received reports from "multiple jurisdictions" of such attacks being conducted against public-sector organizations. Private businesses have been affected as well, including financial organizations and hospitals.
The attacks appear to be part of an extortion scheme in which criminals phone organizations and pose as collections agents seeking payment for a bogus debt of $5,000.
The initial callers are described as having "a strong accent of some sort," though no potential country of origin has been identified and it's not clear if the accent might merely be a ruse.
An earlier report by the FBI's Internet Crime Complaint Center (IC3) suggests that the callers may also spoof a police department phone number for their outgoing caller ID, in an attempt to convince the victim that a warrant exists for his or her arrest for nonpayment of the fake debt.
When the victim refuses to pay, the caller launches a TDoS in retaliation. The report says the attacks last "for intermittent time periods over several hours," during which they might stop for a few hours and then resume. Worst of all, the attacks will sometimes persist for weeks or even months, with the call bombardments coming at seemingly random times.
The report speculates that government and public safety organizations are being targeted by these attacks because functioning phone lines are essential to their operations.
The FBI says victims of such attacks shouldn't pay the blackmail. Instead, they should report all incidents on the bureau's IC3 website. Reports should include as much information as possible, such as dates and times that calls were received, originating phone numbers, any account numbers offered for receipt of payment, and any other information that can be obtained about the callers and their place of origin.
"Additional insight into the scope and impact of the event – specifically how many communications centers have been attacked is critical to identifying the true scope of this occurrence," the bulletin states. ®