Banks, which generally have to absorb the loss, do not want to challenge the cardholder, "who's making valid and profitable transactions at other merchants," Mr. Robertson added.

The ability of this trojan to perform man-in-the-middle attacks on valid transactions is what is most worrying.

This includes valid transactions where all data is correct and invalid transactions that have invalid or missing elements.

Non-ECRS processes typically import valid transactions only and generate an exception list of the invalid transactions.

"It is a perfectly normal, perfectly valid transaction," Mr. Giuliani said.

A valid legal transaction cannot be annulled because of an invalidating factor that came into being afterwards.

The essence of the remedy is that there should be a valid legal transaction from which the court will in certain circumstances grant relief by avoiding it ab initio.

If there was a kinyan, a valid transaction.

Both can work having a valid transaction.

Often, these private entities decide that it is simply not worth the risk of violating sanctions to continue facilitating even perfectly valid transactions.