Nissan said it found malicious software on its network that stole employee user IDs and hashed passwords, but said no personal information or e-mails appeared to have been compromised.

The car company released a statement on April 20, one week after the intrusion was detected. Jeff Kuhlman, Nissan's head of global communications, said on Thursday that Nissan delayed disclosing the breach sooner in order to cleanse its network of the malicious software and prevent tipping off the hackers.