Lookout, which makes cloud security apps for mobile devices, noted in a December blog post that, on average, 80% of consumers have had their emails leaked onto the dark web. You could easily be among that majority without even knowing it.Those leaked emails often lead hackers directly to your passwords for other online accounts and identity theft, Lookout said. Here's the company's list of the 20 passwords most commonly found on the dark web, due to data breaches: 123456 123456789 Qwerty Password 12345 12345678 111111 1234567 123123 Qwerty123 1q2w3e 1234567890 DEFAULT 0 Abc123 654321 123321 Qwertyuiop Iloveyou 666666If you use any of the above passwords for any of your online accounts, you'd be wise to swap them out for something more secure. Cybersecurity experts often recommend picking something longer than the minimum number of recommended characters, and using uncommon characters – like punctuation marks or other symbols – in place of letters and numbers, to make your password harder to guess.Lookout also noted that the majority of people reuse passwords for multiple accounts, which is a practice you should avoid whenever possible. If hackers can get into one of your accounts, you can at least make it harder for them to get into the rest of them.You should also figure out which pieces of information about you and your family are publicly available, and avoid using passwords that include that information – including birthdays, anniversaries, names of loved ones and even your hometown.The U.S. Commerce Department's National Institute of Standards and Technology also recommends screening your passwords against online lists of compromised passwords and using multifactor authentication, among other security tactics.