ACI Worldwide Fraud Monitoring Software Aids in Early Detection of CardSystems Breach.

OMAHA, Neb. -- ACI Worldwide (Nasdaq:TSAI), a leading international provider of enterprise payment solutions, today announced that its ACI Proactive Risk Manager(TM) software helped National Australia Bank (NAB) detect the recently revealed security breach at CardSystems Solution before any other bank or financial institution. NAB, an ACI Worldwide customer since 2000, is the Australian arm of the National Australia Bank Group, whose retail operations extend to Europe and New Zealand. The Australian operation serves 3 million customers.

Australian Treasurer Peter Costello recently told Parliament that National Australia Bank was actually the first bank in the world to uncover the fraud.

"It was the NAB that uncovered this fraud out of all the domestic and international banks of the world and reported it to MasterCard and Visa in September 2004," said Costello.

In his report, Costello specifically highlighted the risk of the CardSystems breach to all Australians who had either traveled to the U.S. or used their credit cards to buy goods online from America.

National Australia Bank uses Proactive Risk Manager to score and monitor all aspects of fraudulent activity involving lost, stolen or counterfeit cards as well as skimming and other types of fraud. The software combines the power of expertly defined rules with a customized neural network model for fast, accurate and flexible response to card fraud. Through its patented technology, the product compares the characteristics of each transaction with the custom fraud model and recorded patterns of behavior for each cardholder. It then assesses and scores the risk for each transaction and sends alerts to reviewers. Users like NAB can develop their own rules and can update models in-house as often as necessary.

Prior to licensing the ACI solution in June 2000, the bank used a largely manual system to detect fraud. Derren Jones, who manages fraud operations for NAB, said "Australia is not suffering significant amounts of credit card fraud, yet geographically we sit on the cusp of one of the major centers of fraud in Southeast Asia."

"Proactive Risk Manager provides us with the ability to closely monitor our cardholder's transaction patterns as they happen and, at the same time, gives us unfettered access to historic transaction data," said Jones. "These features, combined with our skilled staff, enable us to detect fraud early and to take effective counter-measures to protect the bank and its customers."

About National Australia Bank

National Australia Bank is an international financial services organization that provides a comprehensive and integrated range of financial products and services.

The National traces its history back to the establishment of The National Bank of Australasia in 1858. National Australia Bank Limited is a public limited company, incorporated in Australia on June 23, 1893 and now operates the retail bank brands of the National Australia Bank (Australia), MLC (wealth management services), Bank of New Zealand (New Zealand), Yorkshire Bank, Clydesdale Bank and Northern Bank (United Kingdom).

More information can be found at www.national.com.au.

About ACI Worldwide

Every second of every day, consumers are initiating electronic payment transactions--getting cash at ATMs, using debit and credit cards to make purchases in stores and on the Internet, banking by phone and PC, and paying bills online. Over 50 billion times a year, ACI software is used to process these transactions, powering the world's online payment systems. ACI was founded in 1975 and pioneered the development of applications and networking software for online transaction processing. Today more than 500 customers in 78 countries use ACI supplied software. Visit ACI Worldwide on the Internet at www.aciworldwide.com.

Any statements in this press release regarding projected results are preliminary and "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. In addition, this press release may contain other forward-looking statements including statements regarding Transaction Systems Architects, Inc.'s ("TSA"), its subsidiaries or third parties' expectations, predictions, views, opportunities, plans, strategies, beliefs, and statements of similar effect. The forward-looking statements in this press release are subject to a variety of risks and uncertainties. Actual results could differ materially.

For a detailed discussion of these and other risk factors, interested parties should review the Company's filings with the Securities and Exchange Commission, including the Company's Form 10-K filed on December 14, 2004, the Company's Form 10-Q/A filed on February 18, 2005, and the Company's 10-Q filed on May 10, 2005.