Several cases of corruption in the military ranks have revealed a dangerous vulnerability in the nation's security, ABC News has learned.

Dozens of active and former soldiers have abused their military uniforms and authority in a drug smuggling ring, government sources tell ABC News.

A U.S. army sergeant fighting the war on drugs in Colombia was recently sentenced to six years in prison for using military aircraft to smuggle cocaine into the United States.

In April, an Air National Guard pilot and a sergeant used a C-5 Galaxy military transport plane to sneak nearly 300,000 ecstasy pills from Germany into New York.

In another case, three U.S. airmen were arrested in March for stealing military-issue bulletproof vests from Moody Air Force Base in Georgia and selling them to drug dealers for $100 dollars each.

Chip Burrus, the deputy assistant director of the FBI's criminal division, says the corruption "has the potential to be a cancer that spreads in individual units."

The FBI has launched a major initiative to find out whether other members of the military and law enforcement are willing to engage in similar behavior for profit.

Drugs, Bribes, and Military Equipment

Two recent government stings paint a disturbing picture.

"We simply cannot protect the American people if those who are sworn to protect us join and conspire with our enemies," John Richter, U.S. Attorney for the Western District in Oklahoma, said during a press conference.

Last week in Oklahoma, seven current and former U.S. soldiers -- most of them military police -- admitted they received bribes of $2,000 to $8,000 to smuggle cocaine.

"They abused everything that the military has worked for 220 years to uphold, everything that law enforcement works to uphold," said FBI special agent Chip Burrus. "They used their squad cars, they used their Humvees, they used their military vehicles, they used their passes, they used their uniforms."

In Operation Lively Green, FBI agents posed as drug dealers and with $220,000 in cash, enticed Arizona National Guard soldiers, an Arizona police officer, an immigrations agent, and a federal prison guard to help them smuggle more than 1,000 pounds of cocaine into the United States.

In one case, the suspects met a plane on a remote airstrip near Benson, Ariz., offloaded 60 kilograms of cocaine, and drove it to a Phoenix resort hotel in their Army Humvees.

In another case, a U.S. immigration officer at the Mexican border near Nogales, Ariz., waived through a truck he was told was full of cocaine. He and 31 others have admitted they were willing participants in the scheme. They also implicated other officers.

The FBI says to expect more arrests.