A former AMP contractor has pleaded guilty to illegally access of personal details of customers.

Police were brought in last year after IT staff at AMP identified suspicious activity on its systems.

The breach was linked to 28-year-old Chinese national Yi Zheng, who was from work, had his access to customer databases blocked, and has now faced court.

He was accused of downloading AMP customers’ documents and sending them to his personal email account.

AMP says its cybersecurity systems were able to protect customer data.

“These systems worked effectively in identifying a potential issue and we moved swiftly to protect our customers, alerting NSW Police,” the company said in a statement.

“The data breach involved a very small amount of customer information and we have no evidence this data has been further compromised. We are continuing to monitor this closely.”

Zheng was arrested at Sydney International Airport trying to board a flight to China last month.

Authorities seized mobile phones, SIM cards, a laptop and electronic storage devices for forensic examination.

He was charged with possessing identity information to commit an indictable offence.

Zheng's lawyer William Chan entered a plea of guilty on Thursday so that the matter can proceed to sentence.

AMP has contacted all affected customers in December, imposed extra security controls, and notified the relevant regulators.

Some critics say this is on the lower end of AMP’s issues, since revelations from the banking royal commission that AMP has charged customers for advice they never received, and in some cases, charged fees to customers who had died.