The employees who help you run your small business may also be helping to destroy it.

Though they usually don’t mean to do any harm, employees are increasingly responsible for network security breaches, according to an article in Monday’s Wall Street Journal. This is because hackers have gotten adept at breaking into company networks by exploiting well-intentioned employees.

Contrary to what you might expect, the problem isn’t limited to large firms. As previously reported in the WSJ, hackers are expanding their sights beyond multinationals to include any business that stores data in electronic form. In fact, since many small businesses have made the leap to computerized systems and digital records in recent years, they’ve become hackers’ main target.

The good news is that small-business owners and their employees may be able to prevent cyber attacks by learning about what causes them in the first place. For example, if you didn’t already know that many personal email services lack strong protection against malware and phishing, you might want to rethink letting employees check their personal email from your office computers.

This article was written by Sarah E. Needleman and published in The Wall Street Journal.