Target's board of directors came out swinging just days after proxy adviser Institutional Shareholder Services recommended that the retailer oust seven of its 10 members.

In a letter to investors filed with the SEC, Target board interim chairwoman Roxanne Austin mounted a defense of the board's actions before and after a storied data breach exposed the personal information of as many as 70 million customers, the Minneapolis/St. Paul Business Journal reported Monday. She explained that Target had doubled its information security force in the past five years and had invested heavily in network security technology.

Post-breach, the company has advanced plans to adopt chip and PIN technology and has restructured its security and compliance group, bringing in a new CIO and an interim CEO. Austin will learn if she and other board members will retain their positions on June 11 at the retailer's annual meeting.