Are you using Linkedin to stay in touch with colleagues? Maybe you tried creating a blog on Tumblr a few years ago or a Myspace page several years before that. Unfortunately, all three have been the subject of massive account breaches and usernames and password hashes from those accounts are now being traded on the Internet. Hackers are already using this information to attempt to reverse engineer passwords and break in to email accounts, eBay, Amazon.com, and banking websites.

These account breaches underscore the dangers of password reuse. If you have (or had) a Myspace, Tumblr, or LinkedIn account, change that account password and change the password to any other account(s) that are set to the same thing. Email accounts are especially important since they are commonly used as a mechanism for resetting passwords to other online accounts.

You can learn more about how hackers reverse engineer passwords from hashes at https://www.wired.com/2016/06/hacker-lexicon-password-hashing/