The Equifax data breach, in one chart

More than half of Americans may have had their social-security numbers exposed in the Equifax Inc. data breach, and that is just the start.

Equifax EFX, +0.11%  disclosed the shocking data breach a year ago, on Sept. 7, 2017, but it took the company until May 2018 to fully catalogue and disclose the personal information it believes was accessible to network intruders, with help from FireEye Inc.’s FEYE, +1.31%  Mandiant unit. The company disclosed these numbers of affected Americans to the Securities and Exchange Commission after months of investigation.

Even that was not all, however, as Equifax also disclosed that more than 50,000 pictures of government-issued identification, used in credit disputes, had been accessed as well. Equifax has also disclosed that residents of other countries were affected.

Equifax stock was hit hard immediately after the breach was disclosed, but has largely recovered. As of the end of trading Thursday, the company’s stock had declined 4% in the past year, while the S&P 500 index SPX, -0.22%  gained 16.7% in that time and main rival Transunion TRU, -1.17%  increased 55.8%.

Equifax has also disclosed that the breach ended up costing the company roughly $300 million in non-recurring costs, though most of that total was spent on reshaping the company’s security plan and information technology efforts, which apparently needed it.

“We now expect total gross non-recurring spending related to the cybersecurity incident in 2017, principally non-recurring project costs related to our IT transformation and security plan ... as well as legal and other professional fees, to be approximately $300 million,” Chief Financial Officer John Gamble said in Equifax’s most recent earnings conference call, in July. He added that insurance would cover about $75 million of those costs.

Equifax has not seen a slowdown in its business, which mostly relies on the companies that seek its data on potential customers instead of the people whose data the company warehouses. Through the first half of the year, Equifax’s adjusted profit declined by a nickel a share from the year before — about 1.6% — while revenue has increased about 3.2%.