CISI staff and cyber experts have worked around the clock since the attack was uncovered late last week and this morning the CISI website was back up and running, although credit card transactions are suspended for the time being.
The CISI has launched an investigation after the website attack saw 1,000 customers and members exposed to the risk of credit card fraud.
Financial Planning Today understands that a criminal gang from overseas may be responsible for the "highly organised" attack, based on initial findings.
The issue came to light when some members reported “fraudulent activity” on their credit cards following recent payment made through the CISI website.
The CISI website was closed temporarily due to the attack.
The organisation, which provides the Certified Financial Planner and Chartered Wealth manager designations, has launched a major investigation with help from its insurers and KPMG.
The body has contacted 5,785 customers that processed a payment transaction through its website between 1 February 2020 and 15 April 2020.
It said not all of these have seen “fraudulent activity” but it anticipates about 1,000 could have been exposed to a risk of fraud.
The CISI said that if any member identified fraudulent activity they should contact their country's national fraud and internet crime reporting agencies.
In the UK this is Action Fraud, who can be reached on 0300 123 2040 or via www.actionfraud.police.uk