CHARLOTTE, N.C. - Security experts said odds are good that you may be affected after 1.2 billion unique usernames and passwords were stolen in an enormous data breach.
When Jacque Greenway heard about the largest known security-breach in history, she immediately alerted colleagues at Carolina Surgical Clinic.
"I allowed them opportunities to call home, and to call their banks and at least their financial institutions to be reassured the rest of the day," Greenway said.
Read more: 7 ways to create better, stronger passwords
Security experts said a Russian cyber-gang stole more than a billion user names and passwords, and injected malicious code into at least 420,000 websites to get the data.
The websites have not been identified, but reportedly include the auto and food industries, software firms and hotels.
"There's ample reason for people to take action, both individually and perhaps as a business owner," Innovative Network Computer Solutions vice president Eddie Clark said.
Clark works with about 100 businesses on computer support and security. He said a handful contacted him with concerns about the breach. His biggest advice: "Everybody should go out and change their passwords."
Beyond that, experts said you should mix it up by creating passwords that are 10 characters or longer, and include symbols and numbers. Also, use a unique password for each account.
Split social media and money: Do not use the same password for credit cards and bank accounts that you use for other websites.
Potential victims can register with holdsecurity.com to see whether their email addresses are among those compromised, free of charge.