Two US banks that sued Target US security firm Trustwave over responsibility for one of the largest data breaches on record have dropped their lawsuit.

Trustmark National Bank and Green Bank NA said they would dismiss their cases "without prejudice to re-filing," according to filings on Friday and Monday in the federal court in Chicago.
The banks had accused Target and Trustwave of failing to properly secure customer data, leading to the theft of about 40 million payment card records and 70 million other records during last year's holiday shopping season.
But on the weekend, Trustwave CEO Robert McCullen told clients Target did not outsource data security to his company, nor did Trustwave monitor Target's network or process its cardholder data.
Neither Target nor Trustwave would confirm whether the companies have been partners.
A lawyer for Trustmark and Green Bank did not immediately respond to requests for comment.
Trustmark and Green Bank had accused Trustwave of having failed to bring Target's computer systems up to industry standards, and as late as September 20 finding "no vulnerabilities."
The lawsuit said the breach cost banks money from having to correct fraudulent charges and reissue cards, and that the industry could end up owing more than US$1 billion.