The economy may be struggling but the fraud business is booming. Although comprehensive data aren’t kept, the fingerprints of a crime wave are all over. Fraud and identity-theft complaints tracked by the Federal Trade Commission topped 1.2 million last year, up 19 percent over 2010 and 800 percent since 2000.

Moreover, the FBI says fraud involving investments, mortgages, and the Internet is growing. Government takedowns of multimillion-dollar schemes are common.

“Fraud is as high as it’s ever been, because the scam artists are using brand-new channels and technology that didn’t exist 15 years ago,” says Martha Deevy, director of the Financial Fraud Research Center at Stanford University’s Center on Longevity. The center estimates the measurable direct cost of financial fraud to Americans to be $40 billion to $50 billion a year.

Experts also say the need for law enforcement to pursue terrorists has shifted FBI resources from fraud cases. “After 9/11 the scammers realized, ‘This is our time,’” says Doug Templeton, chief investigator for the Pinellas County (Fla.) Department of Justice and Consumer Services, who has tracked criminals in the state for 13 years.

David Vladeck, director of the bureau of consumer protection at the FTC, says, “What we’re seeing is ‘last dollar’ fraud aimed at taking the last dollar from the unemployed or underemployed.”

Like a good novel, a scam is all about the story. It must be convincing and, above all, new. Consequently, con artists change their techniques to respond to changing consumer awareness, says the latest threat assessment by the International Mass-Marketing Fraud Working Group.

We interviewed experts, scoured the complaint files of regulatory and consumer-protection agencies, and followed our readers’ tip-offs to present the latest frauds making the rounds—and some of the classics. Here’s what to watch out for.

A new twist on the home-improvement scam targets folks who want to cut their energy bills with rooftop solar panels or windmills. Solar energy, of course, can reduce your electric bill. But making the big up-front investment is the equivalent of paying for 30 to 40 years of electricity in advance. And lots of variables can confound payback, including living where cloudy weather is commonplace or in the shadow of towering trees, terrain, or nearby tall buildings.

Solar-panel scams. Consumers unfamiliar with those caveats give double-dealers an opportunity to lowball costs and talk up savings. The promised best-case scenario can lure you into paying a big deposit to a contractor who skips town or otherwise never delivers the system or savings. Some victims have been burned for several thousand dollars. Home-improvement companies are the third most complained about businesses, according to the latest survey of consumer-protection agencies by the Consumer Federation of America and the North American Consumer Protection Investigators.

Protect yourself: California is the leader in residential solar, so go to itselectric utility website to see whether solar makes sense for you. If it does, work only with licensed contractors specializing in solar installation. Conduct an energy audit and get bids from at least three companies. Check their Better Business Bureau rating and references. Never pay the full price up front or a deposit of more than $1,000 or 10 percent of the project price, whichever is smaller.

Some scoundrels fly under the radar via telephone. A tech-support person, purportedly from a trusted company like Dell or Microsoft, calls to warn you that its security systems have remotely detected a virus on your computer and offers to remove it—for a fee of $100 or more.

Bogus tech-support scams. Of course, there is no virus, so you pay for unnecessary service. The crook may also take the opportunity to install mock antivirus software that later starts “finding” nonexistent malware. That can cost you a bundle for removal. Worse, the tech may also install software that scans your computer to steal your passwords and hijack your computer to generate ads and spread spam.

Protect yourself: See ourJune 2012 report on security software to find legitimate antivirus and antimalware software that we’ve rated, install it on your PC, and keep it up to date. Hang up on anyone outside your home who claims to find trouble on your PC.

You get an e-mail notifying you about airline reservations you didn’t make, a package from UPS you weren’t expecting, or a problem with your bank account. Just click on this link or attachment.

Phishing and malware scams. If you follow the instructions, you might end up downloading malware designed to take control of your computer and turn it into a spamming robot, harm it with a virus, or mine your files for financial information. Following the link will take you to a site that looks real but is fake. When you log in, it captures your user name and password so that the bad guys can get into your real accounts.

For years, those threats were limited to your PC, which should be protected with security software. But the popularity of smart phones has opened the door to “smishing.” (The word combines “SMS,” or short-message service—aka text messaging—and “phishing.”) Some smart-phone users don’t realize that their phone is a computer and prone to the same security risks as a PC.

Those deceptions work. More than 9 million households had at least one member who gave up information to phishers, and 30 million suffered a malware attack in the previous year, according to our latest survey of online households. The Better Business Bureau pegged phishing as its top scam of 2011. Moreover, today’s fake sites are more believable than ever.

Protect yourself: Never click on a link to your online accounts through e-mail or call an account-related phone number in a text message someone sends you. Instead, open your PC or mobile Web browser and type in the desired address on your own. And don’t click on an e-mail attachment unless you’re expecting it.

In this new bamboozle, burglars claiming to be from a local store call to tell you that you’ve just won the prized plastic, and you must come in to pick it up.

Burglary. The game is to get you out of the house so that robbers can carry out an old-fashioned break-in while you’re gone.

Protect yourself: This simple trick works because it catches you by surprise. Always be suspicious when someone promises you something for nothing. The Better Business Bureau, which first warned about this scam, advises “winners” to ask questions: What contest did I win? How was I chosen? Call the store to independently confirm the details. After you determine that it’s a scam, notify the police. And take extra precautions to lock up your house, set your alarms, and protect valuables when you do leave, since burglars have clearly targeted your home.

Social-media networks are fertile ground for fakery. You might have received, for example, news-feed messages from Facebook friends raving about an app that claims to let you see who’s checking out your profile. Such messages can be spam in disguise, leading to “bait pages.” Other bait involves purportedly bizarre or salacious videos. Consumers who take the bait never get the promised software or film.

Instead, the link drives the curious to a fake Facebook website. You’re asked to “like” the app or other bait, which forwards the spam to all of your friends. Then you have to complete a survey, which collects personal information and opinions.

Survey scams. The goal is to trick you into filling out surveys for online advertisers, with the person who set up the operation collecting commissions for each one completed by an ever-expanding circle of friends, says Chet Wisniewski, senior security adviser at Sophos, an information security firm. One “clickjacker,” Adscend Media of Wilmington, Del., raked in a significant amount of money, according to a lawsuit filed by the Washington state attorney general. The case was settled in May under a consent order in which the company agreed to stop certain marketing.

There’s a difference between scam surveys and legitimate surveys, like those Consumer Reports e-mails to subscribers. Our surveys link you directly to the questionnaire; you don’t need to “like” us first. And your responses are confidential; they aren’t used for marketing or fundraising.

Protect yourself: Don’t reveal personal information online to anyone who initiated contact with you unless your trust is certain. Look for the survey company’s name and go to its website independently by reopening your browser, or call it. Ignore product promos from Facebook friends. Use caution in granting access to your profile. And think before you “like.”

Who doesn’t want to cut sky-high credit-card interest costs in today’s low-rate environment? An unsolicited caller falsely implying that he’s affiliated with your credit-card issuer offers to reduce your interest rate and save you $2,500. The service costs $695 up front, and you must fill out a “financial profile form” with details about your debts, including balances, credit limits, interest rates, and customer-service numbers, plus your name, address, and Social Security number.

Credit-card interest rate-cut scams. The full extent of the “service” typically involves a conference call with the thief, victim, and creditors, during which the shark asks for a rate reduction and the creditor usually refuses. Consumers, of course, can do this on their own—free. One such operation, Select Personnel Management, a Canadian company, and eight associated companies and defendants were ordered by a U.S. District Court in Illinois in 2009 to pay more than $7.8 million and stop telemarketing after the FTC said they hoodwinked more than 12,000 consumers.

Protect yourself: Don’t give personal information such as account numbers to anyone who initiates contact with you. Go todonotcall.gov or call 888-382-1222 to register your phone numbers on the National Do Not Call Registry. Hang up on unsolicited telemarketers.

Investment advisers, broker-dealers, and people from other financial-services firms invite wealthy seniors to enjoy fun, food, and access to investment secrets that will add $100,000 to their net worth, get them 40 percent investment returns, or turn $100,000 into $1 million for their heirs. Attendees might receive a sleeve of golf balls or even win golf clubs.

Investment-seminar scams. The main goal of this educational “opportunity” is to sell investment products that generate commissions for promoters, mostly annuities, real-estate investment trusts, mutual funds, and reverse mortgages. That’s all perfectly legal.

But the ads, sales materials, and pitchmen can be misleading or promote strategies inappropriate for seniors. Reported problems have included promises of a 38 percent rate of return with no risk, the liquidation of investments without the customer’s knowledge or consent, the misappropriation of customers’ funds to buy unregistered oil and gas partnerships, and the sale of nonexistent investments to pay a salesman’s personal expenses and trading losses.

Protect yourself: Deal only with long-time, trusted financial advisers, never with new “friends” from a rubber-chicken sales seminar. Accept the invite and fun, but provide zero financial information and don’t sign blank authorization forms or anything else. And just say no to follow-up one-on-one meetings that will probably be suggested on the pretense of preparing a financial plan.

The Supreme Court’s June ruling upholding most of the Affordable Care Act is expected to revive this scam, which appeared after the legislation was passed in 2010. An “emergency broadcast” and video of President Obama discussing health care prompts viewers to call a toll-free number to reach one of many telemarketers. They imply that they’re selling affordable, government-authorized health insurance that provides “significant” savings on prescription drugs, doctor and hospital fees, and labs coast-to-coast.

Medical discount plan scams. The product isn’t insurance; it’s a discount card costing an enrollment fee of $29 to $500, plus monthly fees of $90 to $1,300. That’s deceptive enough, and the FTC has taken action against more than 50 such operators in recent years. But when ill customers finally need to use the card, many health-care providers don’t honor it. Refunds? Fuggedaboutit!

Protect yourself: Discount plans aren’t illegal, but we consider them to be junk insurance. They’re often sold deceptively as insurance, but unlike real health coverage, discount plans don’t pay any of your medical bills. Instead, they amount to a list of providers who may be willing to offer plan members a discount. Think coupons, not coverage, and this poor bargain becomes obvious.

When a car is unlikely to pass a state smog inspection, a technician or other mechanic simply tests a stand-in car that does meet standards, and voilà! The good numbers are used to certify the belcher.

Auto-repair scams. They continue to thrive; auto-repair rip-offs were No. 8 in the BBB’s complaint rankings in 2011. Among the most common tricks: Mechanics give a good estimate up front but pad the bill with extra work. Some shops make a business of this by advertising a low-priced oil-and-lube job to suck in customers, then “finding” much more expensive problems that need to be fixed.

Another scam involves counterfeit, used, or substandard parts used in place of the new parts you pay for. Sometimes the mechanic doesn’t provide any replacement parts and doesn’t do the work. Bogus billing can add up. After a mechanic in Palm Desert, Calif., claimed to have rung up more than $11,000 in parts and labor on one car, inspectors from the California Department of Consumer Affairs Bureau of Automotive Repair said they found something else: fraud.

Protect yourself: The Coalition Against Insurance Fraud says you should always get a written estimate before work is done, ask to see the repairs and discarded parts, use a shop recommended by knowledgeable friends, check the shop’s BBB rating and Yelp page, and be wary if the mechanic says he’ll help “waive” the deductible on insurance-financed repairs.

Hot electronics are commonly used to entice victims into a shakedown. A pop-up ad on your computer invites you to bid on an iPad, laptop PC, or wide-screen TV, but you must include your cell-phone number to play. Submitting your bid sends a text message to your cell phone that, whether you respond or not, may authorize an unwanted $9.99 a month subscription to some useless service. The charge gets tacked onto your cell-phone bill, where you’re unlikely to notice it.

Cramming. The auction is smoke and mirrors designed to capture your cell-phone number to place unauthorized charges on your bill, a practice called cramming. Unlike numbers for landlines, cell-phone numbers aren’t published in directories, so scammers must be underhanded to get it.

Cell-phone companies, which can collect $1 to $2 commissions per charge, claim that wireless cramming isn’t a problem. But we found 480,000 alleged cell-cramming victims in one case, and in 2011 a Senate committee investigation concluded that landline and cell-phone crammers could be fleecing $2 billion a year from consumers.

“We have multiple wireless-cramming investigations under way,” says Vladeck at the FTC, “and we’re quite quickly seeing the migration of cramming from landline to wireless phones.”

Protect yourself: Guard your cell-phone number like a credit card; don’t give it to strangers. Demand refunds from your cell provider if you’ve been crammed. Tell your wireless and landline carriers to block all third-party billing to your account, and check previous bills for cramming charges.

You receive an e-mail that alerts you to a website—not the manufacturer’s—where you can purchase high-value coupons. They’re not your typical 25 cents off but special coupons for $2 to $60 off or free high-priced products like shaving razors, pricey pet food, diapers, infant formula, coffee, and even restaurant meals. Such giveaways are rarely circulated, but manufacturers do use them to introduce new products or as a goodwill gesture to win back a wronged customer.

Coupon scams. Problem is, there’s no way anyone can accumulate enough of those rare coupons to make a business of it, “so they have to be counterfeit or stolen,” says Bud Miller, executive director of the Coupon Information Corporation, an industry group that works to stop coupon fraud. Other coupon flimflams involve moneymaking ventures based on inflated earnings promises, in which consumers invest several hundred to several thousand dollars for coupon booklets that are difficult to sell, or they toil at work-at-home coupon clipping.

Protect yourself: Avoid such coupons.

It’s the phone call every grandparent dreads: Bad news about a grandchild coming in the middle of the night. Maybe the car has broken down or been involved in a crash, maybe the kin has been unjustly arrested, or a family member in the military has been mugged overseas while on leave. The caller may attempt to impersonate the grandchild or a police officer, lawyer, or doctor. Whatever the details, the family elder needs to wire money ASAP.

Grandparent scams. The caller, however, is not a relative but a cheat who’ll collect the untraceable wire transfer you might send, typically to Canada, Mexico, or another country. This dirty deal has been working since 2008 at least, but the Internet Crime Complaint Center reports that scammers have lately become more sophisticated by mining social-networking sites for personal details that make their impersonation more credible. One couple was pinched first for $3,000 when their “grandson” was supposedly caught fishing in Canada without a license, then for a whopping $30,000 more when the drama escalated to Mounties finding drugs and alcohol on the boat, the Michigan attorney general said.

Protect yourself: Ask for details about your last visit that your grandkid should recall and a stranger couldn’t. Jot down the caller’s location and number. Hang up, and instead of calling Western Union, call the grandchild’s parents or the number you usually use to reach him to verify his whereabouts—even if the caller pleads, “Don’t call my parents!” Don’t send a dime unless you confirm the story.