"During an attack on the IOTA network in October, some funds were found to be at risk of theft, due to users re-using their private keys. The IOTA team took the decision to protect IOTA token holders by taking those funds which were at risk into temporary custody through a snapshot.

Once the attack was stopped, the team worked on setting up a process for reclaiming the funds, and sending them back to the rightful owners. This process of receiving and validating the claims has been understandably complicated and sensitive — especially when taking into account the immutability of the IOTA distributed ledger. This effort has required the full attention of the entire core and legal teams of IOTA over the last few weeks. "

Seen at: https://blog.iota.org/claims-and-reclaims-finalization-e692844c505a