3. A trusted partner ends up not being so trustworthy with your data

Another common security error is found among users who assume that it is fine to send sensitive information such as human resources data to business partners or outsourcing services providers, Roop said. This land mine is made worse when the messages are sent unencrypted.

"The land mine is making the assumption that the person at the HR outsourcer isn't going to send the spreadsheet anywhere else or store the data improperly on their unsecured laptop," he said. "This land mine is true whenever sensitive data is shared via e-mail as part of a business process with third parties."

4. Web-based apps can be portals to leaks and thieves

A common behavior that leads to a lot of security problems includes the use of Webmail or allowing workers to access music-downloading and file-sharing services from the company network, said Marcus.

Such Web-based apps bypass your security filters, as in the case of Webmail, or open a channel to the outside that may carry viruses or worse into your organization.

And if your employees take work home, these risks are magnified. If they use your computers and also do personal activities over the Web, those computers could be compromised, Marcus said. If they bring the data home -- via e-mail or a thumb drive -- they risk it getting lost or stolen.

All of these problems can be avoided fairly easily through enforcement of policies that require the use of secure mail clients over VPNs or encrypted channels (in the case of e-mail), or not allowing users to install apps on their work computer or copy data to removable media (in the case of taking work home). Much of this can be managed through security policies and systems management apps. One difficult channel to block is the use by employees of e-mail to send themselves data, though encryption can help.