The cyber attack which occured at the start of October, when Experian's systems were hacked and T-Mobile users' data stolen, has cost Exparian £13.2 million so far, the company said.
The Register's report on the matter also says that there are a couple of class action lawsuits coming up, only adding insult to injury.
The Dublin-based credit services company said the enormous breach of T-Mobile US information was a result of its own systems being hacked, rather than T-Mobile's. It was tasked with processing credit applications to the company.
Following the hack, T-Mobile US decided to ditch Experian and replace it with TransUnion's CSID service for ID theft and credit monitoring, The Register found out. It added that, even though the blame is on Experian, T-Mobile's reputation has still taken the hit.
"Ultimately, T-Mobile's customers aren't going to care where and how the breach occurred – the bottom line is they trusted T-Mobile with their sensitive data and now that trust is broken," Luke Brown, VP at data loss prevention firm Digital Guardian told The Register.
The hack, which happened on September 15, saw user data of more than 15 million people stolen. The data stolen includes names, addresses, birth dates, Social Security numbers, drivers license numbers and passport numbers.
Connecticut’s attorney general said he would launch an investigation into the breach.
Pre-tax profit fell 14 per cent, from $534m to $458m year-on-year, and revenue dropped by six per cent from $2.39bn to $2.24bn. However, on Monday, the company saw an 11 per cent jump to 1233p.