The leak of data is perhaps the most serious corruption threat facing modern law enforcement agencies, which store huge amounts of sensitive information on various computer systems. A single bent cop at a computer can potentially do more damage than the crooked cliques of detectives once hounded out of the force whose tools were typewriters instead of laptops. The leaking of police information can not only compromise a sensitive operation but can cost a life. "I hate any cops who leaks information to crooks. It could be my address they are leaking," one detective familiar with the Two Floors Up operation says. The leaked police information is understood to relate to the nightclub industry. It's believed it had been requested by criminals who hang around at certain clubs where underworld figures regularly rub shoulders with footy players, celebrities and weekend party goers. The discovery of the leak prompted the force's internal affairs investigators to launch their own secret investigation.

It wasn't so much a case of follow the money as follow the files. Whenever any of the state's 13,000 officers accesses a sensitive database or print a confidential document, they leave a digital fingerprint. Soon, anti-corruption investigators began to focus on a computer at the Criminal Investigation Unit of a bustling inner city police station. The activities of the alleged criminals targeted in the April nightclub raids provided other leads. An ex-cop loomed as the potential link between a suspect detective at the inner city station and the nightclub targets. There are dozens of ex-police working in the security industry across Victoria, mostly doing an honest job as private eyes or investigators for insurers. It's a job where hard-to-find information is an incredibly valuable commodity. The temptation to reach back into the police force, where an ex-detective may have trusted mates, is immense. One of the criminal figures involved in the Two Floors Up nightclub is understood to have been offering $1000 per time for officers to check on the police database. It's easy money for those willing to take a risk that could not only cost them their job but land them in jail. Corruption investigations often have a way of unexpectedly expanding. In this case, the detective under suspicion for leaking information soon led anti-corruption officers to a small number of his colleagues busy arranging a coppers' night out.

A decade ago, this might have involved a plan to drink too many beers at a suburban pub. But on this occasion, a well placed source told Fairfax Media that a detective arranged to acquire "some powders". The use of illicit drugs, including cocaine and methylamphetamine, is emerging as a major concern for force command, especially given the potential dangers that could arise when drug affected officers have access to semi-automatic pistols. Then police commissioner Ken Lay said in 2013: "We know these drugs can do strange things with people's behaviours. We are putting our people out on the street with an array of dangerous weapons. It is imperative they are drug free". This concern has led to education campaigns and targeted drug testing. Members suspected to be using illicit substances are now being subjected to drug tests. The numbers are still relatively small, but more and more police are failing these drug tests. In some ways this is unsurprising, given that drug use is so prevalent in the general community.

When they knock off, some younger police are inevitably going to sporting or night clubs, pubs, festivals and gyms where steroid or party drug culture is entrenched. Policing is also incredibly stressful work and some officers will inevitably use drugs as an escape, just as many people use alcohol to deal with pressure. The anti-corruption probe sparked by the nightclub raids appears to have identified a small number of officers suspected to have indulged in some of the "powders" being spoken about. On August 17, five months after the leak investigation was launched, anti-corruption detectives raided several homes across Melbourne and seized a computer from the inner city police station. They also ordered a small number of detectives to undergo drug tests. After Fairfax Media questioned the force on the operation this week, a spokesman confirmed that three detectives and a uniform officer had been suspended. An ex-cop from the private security industry was also arrested and questioned. "The arrests and searches relate to a protracted investigation into the improper release of police information to people not entitled to be in possession of such information, including criminals," the spokesman said.

The detective at the centre of the inquiry is believed to deny wrongdoing and investigations are ongoing. Before he was suspended, it is understood he was seeking a new role in one of the force's most sensitive areas. It seems highly unlikely he will ever get there.