TDOS: Telecommunication Denial of Service

May 14, 2010

Fake phone calls are tying up people’s phone lines and the FBI is investigating.

Audio Transcript

Mr. Schiff: Hello. I’m Neal Schiff, and welcome to Inside the FBI, a weekly podcast about news, cases, and operations. Fake phone calls are tying up people’s phone lines and the FBI is investigating.

Mr. Schorle: “We are getting a lot of calls from consumers that are reporting receiving a large number of strange and unexplained calls on their mobile or land line telephones.

Mr. Schiff: That’s FBI Special Agent Christian Schorle. He’s at the FBI’s Newark, New Jersey Field Office.

Mr. Schorle: “They are describing a scheme that we have identified as Telecommunication Denial of Service, or TDOS. Basically it’s when a personal attacker creates a diversion on the telephone, while what is really happening is they are looting their bank accounts or online trading accounts.”

Mr. Schiff: When did all of this start, and do we have any idea of how much of this is going on across the country? Any possible suspects, groups, organizations?

Mr. Schorle: “The FBI first learned of this scheme through our partnership with private industry. In November of 2009, there was a report out of St. Augustine, Florida where there was a dentist who lost as much as $400,000 from a retirement account from this TDOS. According to our telecommunication partners that are working very closely with the FBI, they are reporting a surge of this activity again, these attacks over the past few weeks, and perpetrators are suspected of using these automatic dialing programs and multiple accounts to overwhelm the land line and cell phone lines of their victims with thousands of calls. We’ve actually got reports of victims from different states all across the country in the past few weeks as we start to look further into this.”

Mr. Schiff: The people doing this have obtained personal information and possibly moving money around to different accounts trying to steal from these people, who can’t report the problem, because the phones are tied up. How are these people doing this?

Mr. Schorle: “Well, the primary goal, what they are trying to do is really just steal the money. FBI has determined these calls, or these TDOS attacks, are serving as a diversionary technique. During these TDOS attacks, the online trading and other money management accounts are being accessed by the perpetrators. And what they’re doing is, once they are able to access those accounts, they are transferring the funds out elsewhere to other accounts. The perpetrators will obtain account information of their victims in some way—and we’re still working with a lot of our partners to determine exactly how that methodology is—and then they will contact the financial institution to change the victim’s profile information, such as e-mail addresses, telephone numbers, or bank account numbers. The purpose of the malicious phone call is to occupy the victim’s phone number on record with the financial institution, so when the institution tries to contact the victim to notify them of the change, they can’t because the phone line is busy. Consequently, the victim has no idea what’s really transpired until it is too late.”

Mr. Schiff: How are these perpetrators obtaining personal information from unsuspecting victims?

Mr. Schorle: “That’s something that we are still working with and we are still working with our local law enforcement partners, the financial institutions, have liaisons that are working with us, and our telecommunication partners to really determine how that’s being compromised.”

Mr. Schiff: Do we know if they are doing it via the Internet at all? Or getting information from breaking into people’s homes? Are there any thoughts or theories right now?

Mr. Schorle: “We think there are some ties to online banking, and at some point whether the victim was suspect of some kind of a phishing scam, or something like that, where there was an e-mail they received, they clicked on or something that they accessed online that possibly put malware on their computer, and that’s what we really think was really the target that gave them access to the account, some kind of malware that these individuals have downloaded. We are really working with some of the victims and the telecommunication folks to identify some patterns and trends, so we can see what the point of entry would have been.”

Mr. Schiff: Is the FBI working closely with the various phone companies and other agencies to solve these problems?

Mr. Schorle: “Yes we are. The FBI has a strong working relationship with many of the telephone companies like AT&T, Paytech, and Verizon, to name a few. Last month the Communications Fraud Control Association, or CFCA, had invited the FBI to become its official law enforcement liaison. The CFCA is located here in New Jersey, and they were formed by a group of security professionals from some of the different telephone companies to establish a cooperative effort to combat the growing problem of communication fraud. And since, they have expanded their membership to include other members of the communication providers, and also law enforcement. The FBI and the CFCA are working together to analyze the patterns and trends of these phone calls to educate the public and ultimately identify the perpetrators and bring them to justice.”

Mr. Schiff: How can the public be more vigilant so that they don’t become a victim?

Mr. Schorle: “Protection from these TDOS attacks and fraud ultimately requires the consumers to be proactive. Consumers should continue to emphasize strong security procedures for their financial accounts, including placing fraud alerts on all their financial accounts with major credit bureaus. If they believe they have been targeted by TDOS or other fraud, they should make sure their passwords for online banking and telephonic banking are changed regularly and frequently. Financial accounts should be monitored regularly, and unknown or suspicious transactions should be reported ultimately to the financial institution to investigate. Personal identifying information such as dates of birth or Social Security account numbers should not be given out through e-mail or to unverified callers that might try to solicit that information from victims. People should also obtain a copy of their credit report on an annual basis and review it for fraudulent activity.”

Mr. Schiff: And if someone thinks they are a victim of this TDOS, what should they do?

Mr. Schorle: “We are urging anyone who suspects that they are being targeted by TDOS to immediately contact their financial institution and harden the security on their accounts. This notification should include online trading brokers with whom the victim might have an account. In one recent case, there was a victim who acted early and was able to alert her financial institution and was able to thwart off any loss of money because of the early notification to the financial institutions. We are also encouraging victims to promptly report the incident to the FBI, to a complaint filed on, which is the FBI’s online cyber crime complaint center.”

Mr. Schiff: Be sure to secure all of your financial credit and banking accounts and change your passwords often. Remember, if you experience these phony phone calls, call your bank or credit union right away and contact the FBI next either by calling your nearest FBI office or on the Internet at That’s our show for this week. Thanks for listening. I’m Neal Schiff of the FBI’s Office of Public Affairs.

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