LastPass Forces Master Password Reset After Detecting Network Anomaly

Online password manager LastPass noticed signs of a potential network intrusion while reviewing its logs and alerted users to the possibility of a server breach. As a precaution, all users are being forced to change their master password.

An "anomaly" in the network traffic has prompted online password manager LastPass to notify its customers of a potential security breach that requires them to immediately change their master passwords.

Administrators noticed a "network traffic anomaly" that lasted a few minutes from a "non-critical" machine on May 3, LastPass wrote on its blog on May 4. Most anomalies generally turn out to be an employee poking around or an automated script executing a process.

After some more digging, the team discovered a matching anomaly in which more traffic was sent from the database compared to what was actually received by the server. The team was able to gauge roughly the amount of data that had been stored, calculated that it was big enough to have transferred user email addresses along with the server "salt and salted" password hashes from the database. The amount of data taken wasn't "remotely enough" to have pulled many users' encrypted data blogs, according to LastPass.

"We're going to be paranoid and assume the worst: that the data we stored in the database was somehow accessed," the LastPass team wrote.

Salts are randomly generated bits of data that is combined with a password before generating a cryptographic hash, which is saved in the database. Using a salt generally makes it harder for attackers to brute-force a password. Using a salt expands the storage and computing power required to create a rainbow table, or a precomputed lookup table containing hash values of dictionary words and a salt. So conventional wisdom says it is not feasible to crack passwords protected in this way. However, there have been recent reports of hackers leasing resources from Amazon EC2 to crack passwords.

As a result, if the user selected a strong, non-dictionary-based password or passphrase for the master password on LastPass, the potential threat is very small because it's unlikely the attacker would be able to brute-force its way to gain access to other accounts, according to LastPass.

"Unfortunately not everyone picks a master password that's immune to brute forcing," the team wrote.

The company doesn't have a lot of information regarding what happened or what attack vector was used. The open source Asterisk phone server was "more open" to accepting network packets than it needed to be, but there were no indications of tampering, according to the blog post. There were also no logs indicating any escalation of privileges for any users in the database.

LastPass is rebuilding the servers in question and has checked the source code for the Website and plugins to ensure they haven't been modified. The team will be rolling out PBKDF2 (Password-Based Key Derivation Function) using SHA-256, a set of set of cryptographic hash functions designed by the National Security Agency, to start storing passwords hashed with a 256-bit salt.

In order to counter the potential threat, everyone must change their master passwords and prove their identity by using an IP address they've used before or by validating the email address by clicking on the link sent to that address. If an attacker had a stolen master password, LastPass still wouldn't give access to this "theoretical attacker" because they wouldn't have access to the email address or the actual computer or mobile device.

"We realize this may be an overreaction and we apologize for the disruption this will cause, but we'd rather be paranoid and slightly inconvenience you than to be even more sorry later," the team wrote.

LastPass is doing the "right thing," Carole Theriault, senior security consultant and Sophos press contact, wrote on NakedSecurity. The company saw something odd, recognized the risk that sensitive information may have falling into wrong hands and acted immediately, Theriault said.

There appears to have been several glitches with email verification. Several users have complained that their primary email password is stored in LastPass and they are unable to retrieve the validation message. LastPass has given instructions on accessing the information in offline mode.

Despite the tagline, "The Last Password You'll Ever Need," the lesson appears to be that users should remember the LastPass master password and the password for the primary email address.

Other users were very critical of LastPass forcing users to click on a link in an email. "Um...this is malware 101. Never click links in emails," a paying customer commented on the post.

This is the second security incident for LastPass in the past few months. A security researcher found a cross-site scripting flaw on the LastPass Website on March 2. The flaw has been fixed.

"I think i'll go back to remembering my passwords myself. This stank of a phishing attack on 1st look," wrote another user, "len."