Password management firm LastPass says the hackers behind an August data breach stole a massive stash of customer data, including password vault data that could be exposed by brute-forcing or guessing master passwords.
The company, which is owned by GoTo (formerly LogMeIn), said the hackers broke into its network in August and used information from that hack to return and hijack customer data that included company names, end-user names, billing addresses, email addresses, telephone numbers, and the IP addresses from which customers were accessing the LastPass service.
In addition, the unidentified actor was also able to copy a backup of customer vault data from an encrypted storage container, LastPass chief executive Karim Toubba said in a notice published on Thursday.
The exposed container contained both unencrypted data, such as website URLs, as well as fully-encrypted sensitive fields such as website usernames and passwords, secure notes, and form-filled data, Toubba said..
“LastPass production services currently operate from on-premises data centers with cloud-based storage used for various purposes such as storing backups and regional data residency requirements. The cloud storage service accessed by the threat actor is physically separate from our production environment,” he added.
To date, we have determined that once the cloud storage access key and dual storage container decryption keys were obtained, the threat actor copied information from backup that contained basic customer account information and related metadata including company names, end-user names, billing addresses, email addresses, telephone numbers, and the IP addresses from which customers were accessing the LastPass service.
The threat actor was also able to copy a backup of customer vault data from the encrypted storage container which is stored in a proprietary binary format that contains both unencrypted data, such as website URLs, as well as fully-encrypted sensitive fields such as website usernames and passwords, secure notes, and form-filled data.
The LastPass CEO insists the encrypted fields remain secured with 256-bit AES encryption and can only be decrypted with a unique encryption key derived from each user’s master password using the company’s so-called zero knowledge architecture.
However, he warned that the threat actor may attempt to use brute force to guess a user’s master password and decrypt the copies of stolen vault data.
“The threat actor may also target customers with phishing attacks, credential stuffing, or other brute force attacks against online accounts associated with your LastPass vault,” Toubba warned.
The company is urging users to avoid reusing master passwords on other websites.
LastPass has also notified a small subset (less than 3%) of its business customers to recommend that they take certain actions based on their specific account configurations.