A hash of LinkedIn passwords was found for sale on an online forum, leading to the discovery that hackers had gained access to the LinkedIn network and stolen users' data, prompting LinkedIn to rebuild servers, force employee password changes, and inform affected users to change their own passwords.
A hacker was able to gain access to around 30 LinkedIn user accounts by cracking the usernames and passwords, and collecting only the metadata of these users' accounts. LinkedIn had to rebuild its servers and forced employees to change their passwords after the incident.