Many companies spend a small fortune and deploy a small army to secure themselves from the many security threats lurking these days. But all those efforts can come to naught when making any of these common mistakes. The results can range from embarrassing to devastating, but security experts say that all are easily avoidable.

And almost all can be done without spending one more cent.

Here are the 10 most common security land mines that experts say you need to avoid.

1. A slip of the finger reveals the company secret

Many of the most prevalent security issues are the result of small technological habits that can easily be avoided.

For instance, imagine how many inadvertent data loss events could be eliminated if more users were instructed to turn off the e-mail address "autofill" feature in Microsoft Outlook and other messaging systems, said Steve Roop, senior director of marketing and products at Symantec.

"When employees are quickly addressing their e-mails, they inadvertently tab and select the wrong name in haste. The employee thinks he is sending an e-mail internally to Eric Friendly, but autofill instead sent it to Eric Foe," Roop said. "We've all done this. [But] if the e-mail contained sensitive data about a proposed merger or acquisition, then the secret is out."

As much as 90 percent of all information leakage events are tied to inadvertent e-mail foibles, including the autofill accidents and mistakes in handling encryption or misinterpreting usage policies, Roop said. Just the simple act of turning off something like autofill could save businesses a lot of headaches at no extra cost, he said.

2. People give away passwords and other secrets without thinking

More often than not, users -- not outside intruders -- are responsible for coughing up the passwords and personal data that allow attackers to break into their computers and their employer's networks to wreak havoc and tarnish their names.

Despite all the education people have been given about phishing, spyware programs, and hacked Web sites, many users are still willing to hand out their data whenever it is requested without checking to ensure that they aren't be duped or misled, said Dave Marcus, security research and communications manager at McAfee. "People assume the legitimacy of sites as presented; this is fundamentally incorrect in a Web world," Marcus said. "The easiest way to steal someone's identity online is simply to ask them for it."