There has been a string of insider trading convictions this year, but many more are being missed.

Investment banker Oliver Curtis was found guilty of insider trading last week, just days after ANZ accountant Michael Hull was sentenced to 17 months in prison for receiving illegal stock tips.

These cases followed the conviction of former managing director of China's Hanlong Mining, Steven Xiao, who was handed an eight-year sentence last year, and former NAB banker Lukas Kamay’s seven-year sentence for a $7 million plot involving an ABS employee.

There have been just 79 cases of insider trading brought before the court since 1973.

Lawyer James Wheeldon, who defended Michael Hull, says a lot of inside trades go unnoticed.

“If you asked most corporate lawyers or investment bankers in Australia if they thought that most cases of insider trading were detected and then successfully prosecuted you'd get a resounding ‘no’,” Mr Wheeldon told reporters.

“There are always going to be people who are looking to structure things either by hiding transactions, using straw purchases, using trusts, offshore accounts, exotic financial instruments, all sorts of ways you can seek to evade detection and there's always going to be a cat-and-mouse game.”

But things have improved since ASIC took over the responsibility for market surveillance in 2009.

“If we look at the last few years, if we look at the period of time from 2009 right through to June this year, ASIC has brought 39 cases,” according to Melbourne University law professor Ian Ramsay.

“Its success rate is now more than 80 per cent.”

Still, ASIC struggles with the burden of proof, and often relies on confessions and whistleblowers.

Regulatory laws are exceedingly complex, and while they carry long sentences, it is rare to actually face time behind bars.

“There's a very high percentage of cases where although an individual offender is sentenced to imprisonment, that actual term of imprisonment is fully suspended,” Mr Ramsay said.