Possible theft through email addresses is expected, huge companies warned on Monday. They told their clients that they should expect to receive an email coming from a seemingly official account coaxing account owners to give their account name and passwords.

About twelve large companies announced over the weekend that hackers may have gained access to their email addresses due to a security breach in Epsilon. Epsilon is a company located in Dallas that manages email communication of many companies.

Some of the companies in question are Barclays Bank, Capital One Financial Corporation, JPMorgan Chase & Company, and Best Buy Company. These are major players with very important client data base.

Epsilon already confirmed Friday that their security system had been breached and email addresses of customers were exposed. They, however, reassured the public that no information – other than email addresses – were accessed by hackers.

However, email addresses are very important tool for spammers, hackers, and thieves. They can use this information to contact bank clients and trick them in to giving up their log-in details. Hackers can also make it seem like those emails are official and are from your bank. If not stopped, you can unknowingly handing these hackers your money.

That breach in security can make the phishing attacks more proficient because email recipients actually have an account with the bank or the company. Phishing is a hacker’s way to acquire sensitive data like credit card details and passwords.

The said incident also caused Epsilon, which has over 2,500 clients, tons of money after their shares fell by 4.45 per cent Monday.