T-Mobile CEO Mike Sievert has issued a statement apologizing for the recent hack that compromised tens of millions of user accounts.

T-Mobile’s systems were compromised in mid-August, with a treasure-trove of personal data stolen and put online for sale. Depending on the accounts in question, the compromised information contained some combination of names, addresses, date of birth, phone numbers, IMEIs, IMSIs, SSNs and driver’s license/ID information.

CEO Mike Sievert has issued an apology to customers, calling the entire ordeal a “humbling” experience.

Attacks like this are on the rise and bad actors work day-in and day-out to find new avenues to attack our systems and exploit them. We spend lots of time and effort to try to stay a step ahead of them, but we didn’t live up to the expectations we have for ourselves to protect our customers. Knowing that we failed to prevent this exposure is one of the hardest parts of this event. On behalf of everyone at Team Magenta, I want to say we are truly sorry.