(CNN) "Buy real Viagra here, for a fraction of the price! Free Shipping included! All without a prescription!" shout the online headlines. A quick Google search brings up a plethora of enticing choices for any consumer looking for a deal on one of the world's most popular prescription medications.

Need beta blockers to bring down your blood pressure? Cholesterol lowering agents? Antibiotics? You name it, you can find it on the Internet. All the popular brand-name drugs are readily available online at discounted prices, and often without a valid prescription.

Many online retailers say they can cut through the red tape that ties up more traditional brick and mortar pharmacies and pass on a substantial savings to the customer in the process.

But before you pop that discounted capsule or tablet in your mouth, you might want to consider the real price of such pills. Chances are, if an Internet pharmacy deal sounds too good to be true, it probably is.

The World Health Organization estimates as many as 50% of illicit online pharmacies are selling counterfeit medications

And in a 2014 annual report, the National Association of Boards of Pharmacy in the United States concluded after sampling more than 11,000 Internet pharmacies that a staggering 96% of those pharmacies did not comply with NABP patient safety and pharmacy practice standards, or state and federal laws, and were deemed by the NABP as " not recommended ."

John Clark, former deputy assistant secretary for the U.S. Immigration and Customs Enforcement agency and now chief security officer and vice president of global security for Pfizer pharmaceuticals, explained that 78 counterfeit Pfizer medications have been found in 109 countries.

The most popular fake? Viagra.

Paint-filled antibiotics?

That heart medication being advertised at a fraction of the price might contain rat poison. The cholesterol lowering drug you are taking could be filled with brick dust. And the antibiotic may be filled with other toxic chemicals such as paint or inkjet material.

Clark said the agency found all these ingredients and more in counterfeit medications it seized, but believed the counterfeiters aren't necessarily looking to poison people. He said it's more about finding the cheapest binding agent they can get their hands on to maximize their profit.

The online sellers are clever, often advertising themselves as Canadian to ease the consumer's mind about the source of the drugs. But many of those websites are phony, and the drugs are coming from counterfeiters all over the world. The countries topping the counterfeit drug manufacturing list are India and China.

Speaking anonymously, with his face hidden, an online seller from Pakistan shared how easy it is to market counterfeit drugs. "We sell all over the world, to America, Europe, China, Iran and Iraq. All over. But we do not take these medications ourselves, nor do we recommend them to anyone we know, because they are not good quality medications."

A counterfeiter in a nearby Pakistani market proudly showed off his operation to CNN. As he picked up bottles and capsules waiting to be assembled, he said, "We prepare whatever is in high demand. But everything is the same, no matter what we call it. We put the very same ingredients in all of these capsules, and the very same syrup in all of these bottles. Only the color is different."

An illegal $431 billion a year industry

The profits are huge. In 2012, the WHO estimated the counterfeit drug trade was a $431 billion a year industry and growing. Since then, according to a report by the Intellectual Property Rights Coordination Center, the WHO no longer provides estimates of counterfeit drugs, "because of the difficulty of providing accurate measurement."

The practice is so widespread it is nearly impossible to track the depth and scope of the fake drug market.

Clark said part of the draw for counterfeiters is the "low risk and high reward. The profit margins are phenomenal, and the industry is highly lucrative. And if the counterfeiter is caught, he or she often receives the minimum sentence" which varies by country and can be as low as a fine and a few days in jail, Clark said.

Efforts to curb the trend

One of the main challenges of curbing the counterfeit trade is "a lack of universal laws that criminalize counterfeit medicine," he said. "Right now it is handled differently country by country."

"There needs to be global governance on this issue," he added.

Clark said Pfizer is assisting law enforcement in preventing counterfeit Pfizer medicines from reaching patients by providing training to authorities in 149 countries, including Pakistan.

There are other signs of progress. From 2010 to 2014, Interpol's Operation Pangea, with support from nations all over the globe, suspended 57,000 illicit online pharmacies and seized more than 30.3 million units of fake medications

Pakistan, like many other countries, has created a special agency, the Drug Regulatory Authority of Pakistan, in an effort to crack down on the problem.

In the United States, the FDA says the 2013 Drug Supply Chain and Security Act, passed by Congress and signed into law by President Obama, "is being implemented over several years, and will require drug manufacturers, re-packagers, wholesale distributors and dispensers to provide product and transaction information with each sale and notify the FDA and other stakeholders of illegitimate products," the FDA said. "This will result in improved detection and removal of potentially dangerous drugs from the supply chain."

Despite these measures, the global counterfeit drug trade is a booming business. With each website that is shut down, with a few simple keystrokes the same seller can pop up again with a different URL.

With estimates of as many as 1 million people dying every year from ingesting counterfeit drugs, the reality remains a deadly one.