It took a group of cyber criminals 19 days to steal the personal information of 40 million people from Target's database, but it will take the retailer much longer to recover from the massive theft. On Wednesday, security blogger Brian Krebs reported that Target (TGT) was investigating a security breach involving stolen credit and debit card information. The retailer confirmed Thursday that approximately 40 million in-store customers had their information comprised over a nearly three-week period that included the heavily trafficked shopping period surrounding Black Friday. The value of the stolen personal information could be as much as $800 million depending on the extent of the criminals' underground network. The security breach represents one of the largest at a major retailer since 2007 when criminals stole card numbers and other data from as many as 90 million cards belonging to T.J. Maxx, HomeGoods, and other discount chains owned by parent-company TJX.