How loyal are your IT workers? The results of a recent survey should make company leaders uneasy.

According to this new survey, that all-important team could be one of your company’s biggest threats.

As demonstrated by the on-going legal saga of Terry Childs, the San Francisco network administrator who was jailed after refusing to turn over critical passwords to the city’s computer system, insiders can wreak havoc on an organization when they put their minds to it – and if they get mad enough.

In this case, San Francisco said the recovery after the incident cost more than $1 million. The city insisted that Childs believed his job was in jeopardy and withheld the passwords to make himself indispensable.

Other examples of this type of threat involve former staffers using access privileges that have yet to be shut down to sabotage the company’s network or steal sensitive information.

Many organizations are at risk of similar events, according to a recent report from security vendor Venafi.

According to the survey of 500 IT pros:

1. 36% said they would be able to hold their company ransom by refusing to turn over encryption keys
2. 31% said if they left the company, they could continue using their privileges to access sensitive information, and
3. 43% said they’d be able to cause havoc for their current employer if they left the company.

What can companies do to protect against those threats? The first key is for IT to avoid situations in which only one employee knows a critical encryption key or password.

Second, privileges should be revoked immediately after some leaves the company. That goes for staffers in the IT department, as well as the rest of the company — IT leaders must communicate with HR so they know right away when someone quits or is fired.

But beyond all this, it’s important to make sure your IT team is staffed with folks who’ve demonstrated their integrity and work ethic. Work with your IT hiring managers to focus on these qualities when they’re interviewing job candidates.

And, as always, make sure you’re a leading example of this kind of behavior. Loyalty and fairness in the way you treat your employees is the best insurance against this kind of behavior.