CHICAGO — Identity theft and fraud have ruined Dave Crouse’s life.

In less than six months, $900,000 in merchandise, gambling and telephone- service charges were siphoned out of his debit card. His attempts to salvage his finances have cost him nearly $100,000 and have bled dry his savings and retirement accounts. His credit score, once a strong 780, has been decimated. And his identity — Social Security number, address, phone numbers, even historical information — still is being used in attempts to open credit cards and bank accounts.

Crouse is among the 11.1 million adults — one in every 20 U. S. adults —last year who have the dubious distinction of breaking the record of the number of identity-fraud victims in the United States, according to a recent study by Javelin Strategy and Research.

“The odds have never been higher for becoming a fraud victim,” said James Van Dyke, Javelin president and founder.

Crouse, 56, can attest to that. Once an avid fan of online shopping and banking, the Bowie, Md., resident would auction on eBay.com, download songs from iMesh.com and use his automatic teller machine card like a credit card.

He first noticed suspicious activity in his account last February — small charges of $37 or $17.98. He had a full-time job then and was spending out of an account that generally held $30,000.

“All of a sudden it really got bad,” he said. “In August, the charges hit big time—$600, $500, $100, $200— all adding up from $2,800 to $3,200 in one day.”

He called his bank immediately and started what began a tiresome process of filling out what he said finally amounted to about 20 affidavits swearing that he was not responsible for the charges. He said he filled out an affidavit about a charge on one day, and the next day the bank had accepted similar charges approaching $4,000.

“At that point I was going to the bank every day and looking at everything,” he said. He had the time then. Five months before that he had been laid off his $180,000-a-year construction- industry job.

Now he was in a double bind: His $2,300-a-week net income had dwindled to $780 in unemployment

checks every two weeks, and his accounts were getting drained daily — even after he closed his debit account.

He opened a new account at a different bank, and the next day both accounts got hit with a $1,100 charge. The new bank told him a keystroke malware probably had done him in. Someone had hacked into a site he visited regularly; his computer got infected and picked up all his personal information by tracking every key he struck.

While much of the fraud came from online purchases and at gambling sites, new accounts were opened in different names but linked to his bank account. A plasma television set purchased from a Best Buy in Florida was shipped to a Brooklyn, N. Y., address. In another case, a woman in North Carolina was writing out checks tied to his account.

“It was nasty,” he said, admitting that he even contemplated suicide. “I just couldn’t take it. I didn’t feel like a man anymore. I was violated, and I didn’t know what to do.”

Michael Stanfield, chief executive of Intersections, a risk-management firm, said identity thieves take an established address and phone number of an identity that “has some value,” like a doctor or a lawyer. In many instances, they can go to the Internet and acquire the matching Social Security number for as little as $50. They then have enough information to get an address changed with your bank account or a credit card account. They apply for new accounts as you.

Others take over established accounts, Stanfield said, through keystroke malware that you — and probably hundreds or even thousands simultaneously — have picked up through the Internet.

Listening software then sits on your computer, perking up when you go to a bank site. It copies all your key strokes — your user name, password, challenge question, account numbers, everything.

“You leave, and the bad guy goes right back in behind you,” Stanfield said. “We’ve seen examples where that has occurred, and its gets fixed, and a month later the computer gets cleaned out again, and he becomes a new victim, even with a new account.

Those most at risk are those who spend the most, and that tends to be middle-income families. Those most likely to miss fraud are usually 18 years old to 24 years old, simply because they don’t pay enough attention.

“The more you transact, the more you’re at risk because you leave a trail behind,” Van Dyke said.

Crouse, who has battled to regain his financial footing, has some advice: Don’t touch Web sites that offer free things or 30- day trials, never give out personal information and always keep your receipts.

Javelin recommends keeping sensitive information from prying eyes, requesting electronic statements, using direct deposit, securing all personal and financial records in locked storage devices or behind a password and shredding all sensitive documents.

It also warns against putting checks in unlocked mailboxes and giving out your Social Security number.

Other recommendations include installing antivirus software on your computer and keeping it updated; never responding to requests for personal or account information online or over the phone; watching out for convincing imitations of banks, card companies, charities and government agencies; not divulging birth date, mother’s maiden name, pet’s name or other identifying and personal information on social media sites like Facebook, Twitter and LinkedIn; being creative with passwords and not accessing secure Web sites using public Wi-Fi.