High-tech thugs have put a new twist on the methods of the malevolent intruder who cuts a home's phone lines so his victim can't call for help.

Now, digital-savvy thieves are dialing for dollars – cleaning out bank and retirement accounts, while holding their victims hostage by making sure their financial institutions' calls to question the unusual activity are blocked by relentless busy signals.

According to the FBI, the thieves use automated dialing systems and multiple accounts to deluge their victim – an individual or a business – with thousands of phone calls ranging from dead air to advertisements to recorded messages.

It's called a "denial-of-service" attack: While the phones are busy, the thieves use the bank account numbers or other personal information they've gleaned from social networking sites or malware (software designed to infiltrate a computer system without the owner's informed consent), to siphon money from accounts by impersonating the victims.

They may get the information from personal information posted on social networking sites, such as Facebook or MySpace, or because their victim responded to a "phishing" email (one designed to appear as a legitimate message from a financial institution or credit card company). They can also get banking account numbers, Social Security numbers or other personal information their victims have given to them over the phone by pretending to be from the victim's bank or credit card company, or by making a too-good-to-be-true-better-act-now sales call or sending a letter informing the victim he or she has won a lottery.

Financial institutions typically contact an account's owner in the event of unusual activity, such as withdrawing all of one's savings or draining a checking account. But if the phone lines are all constantly busy, the victim cannot be reached.

It was after a dentist in Florida lost $400,000 from his retirement account that the FBI learned of this latest scam.

"As of April of this year, there has definitely been a noticeable surge in telephone denial-of-service attacks, with numerous incidents having been reported in several Eastern states," the FBI said in a recent bulletin.

To help fight these schemes, the FBI has teamed up with the Communication Fraud Control Association, comprised of security professionals from communication providers, to analyze the patterns and trends of telephone denial-of-service attacks, educate the public, and identify the perpetrators and bring them to justice.

The FBI warns people to never give out personal information to an unsolicited phone caller or via e-mail, and to change online banking and automated telephone system passwords frequently. It also advises people to check their account balances often and to protect their computers with the latest virus protection and security software.

Anyone who believes they have been the target of such an attack is asked to contact their financial institution and telephone service provider, and to file a complaint with the FBI's Internet Crime Complaint Center at http://www.ic3.gov/default.aspx [1].